Hydraulic Engine

ABSTRACT

An internal combustion engine and method of operating such an engine are disclosed. In some embodiments, the engine includes a piston provided within a cylinder, wherein a combustion chamber is defined within the cylinder at least in part by a face of the piston, and an intake valve within the cylinder capable of allowing access to the combustion chamber. The engine further includes a source of compressed air, where the source is external of the cylinder and is coupled to the cylinder by way of the intake valve, and where the piston does not ever operate so as to compress therewithin an amount of uncombusted fuel/air mixture, whereby the engine is capable of operating without a starter. In further embodiments, the piston is rigidly coupled to another, oppositely-orientated second piston, and the two pistons move in unison in response to combustion events to drive hydraulic fluid to a hydraulic motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Nonprovisional patentapplication Ser. No. 13/400,437 filed on Feb. 20, 2012 entitled“Hydraulic Engine”, which is a continuation of U.S. Nonprovisionalpatent application Ser. No. 12/374,630 filed on Jan. 21, 2009 (now U.S.Pat. No. 8,135,534 issued Mar. 13, 2012) having the same title, which isthe U.S. national phase of International Patent Application No.PCT/US2007/074476 filed on Jul. 26, 2007 having the same title, which inturn claims the benefit of U.S. Provisional Patent Application No.60/833,344 filed on Jul. 26, 2006 also having the same title, and thisapplication hereby claims the benefit of, and incorporates by referenceherein in their entireties, all of the aforementioned nonprovisional,international, and provisional patent applications.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Field ofthe Invention

The present invention relates to engines, and more particularly tointernal combustion engines employing one or more pistons and cylinders,as can be employed in vehicles as well as in relation to a variety ofother applications.

BACKGROUND OF THE INVENTION

Internal combustion engines are ubiquitous in the modern world and usedfor numerous applications. Internal combustion engines are the mostcommon type of engine utilized for imparting motion to automobiles,propeller-driven aircraft, boats, and a variety of other types ofvehicles, as well as a variety of types of motorized work vehiclesranging from agricultural equipment to lawn mowers to snow blowers.Internal combustion engines also find application in numerous types ofdevices that are not necessarily mobile including, for example, varioustypes of pumping mechanisms, power washing systems, and electricgenerators.

Many different types of internal combustion engines have been designedand built over the years. Among the most common such engines are enginesin which one or more pistons are mounted within one or morecorresponding cylinders arranged about a crankshaft, where the pistonsare coupled to the crankshaft by way of one or more connecting rods suchthat linear movement of the pistons is converted into rotationalmovement of the crankshaft. In terms of automotive engines, typicallysuch crankshaft-based engines are “Otto engines” in which each enginepiston repeatedly moves through a series of four strokes (cycles),namely, a series of intake, compression, combustion and exhaust strokes.

Although such conventional, crankshaft-based four stroke engines arepopular and are undergoing continuing improvement, such enginesnevertheless suffer from several limitations. First, the fuelefficiencies that can be achieved by such engines continue to limited,something which is disadvantageous particularly insofar as the world'ssupply of fossil fuels is limited, insofar as demand (and consequentlyprice) for fossil fuels continues to increase, and insofar as concernsover the impact of fossil fuel-based internal combustion engines uponthe global environment continue to grow. The fuel efficiencies of suchengines are limited for a variety of reasons including, for example, theweight of such engines, and frequent operation of such engines in anidling manner when no load power is truly required (e.g., when anautomobile is at a stop light). A further factor that limits the fuelefficiencies of many such engines that employ spark plugs in combinationwith high octane fuels (rather than diesel engines) is that suchengines, in order to avoid undesirable pre-ignition combustion eventsduring the compression strokes of such engines, are restricted todesigns with relatively modest (e.g., 9-to-1 or 10-to-1) compressionratios.

Second, because combustion strokes in such engines only occur during oneof every four movements of a given piston, such engines by their naturerequire that an external input force/torque be applied to impart initialrotational momentum to the crankshaft of the engine in order for theengine to attain a steady state of operation in which the engine (andits crankshaft) is naturally able to advance to successive positions atwhich combustion events can take place. For this reasons, such enginestypically employ an electrically-driven starter motor that initiallydrives the engine until the engine is able to attain its own steadystate of operation. Relatedly, to maintain such steady state rotationaloperation, and also to reduce the degree to which output torque providedby the engine varies as combustion events occur and then pass, suchengines typically require a flywheel that tends to maintain therotational momentum of the engine at a constant level.

Although such starter and flywheel components employed in conventionalcrankshaft-based four stroke internal combustion engines are commonlyused, and well-understood in terms of their operation, the inclusion ofsuch devices within such engines adds complexity and/or significantweight (as does a crankshaft) to the engine that, consequently, canincrease the cost of designing or building the engine, increase thecomplexity of maintaining or repairing the engine, and/or further reducethe fuel-efficiency of the engine. Further, depending upon how effectivethe starter of the engine is in terms of starting the engine, the needfor a starter can further be an impediment to effective (and enjoyable)operation of the engine. For example, it can be particularly frustratingto an operator when a starter mechanism fails or otherwise is incapableof starting an automobile engine in a short amount of time, particularlywhen the operating environment is cold such as during wintertime.

Various other types of internal combustion engines likewise suffer fromvarious limitations that may be the same, similar to, or different fromthe limitations described above. For example, while many of theabove-described crankshaft-based 4 stroke internal combustion enginesare able to run fairly cleanly in terms of their engine exhaustemissions, in contrast many diesel engines as well as conventionalcrankshaft-based 2 stroke engines under at least some operatingcircumstances are unable to effectively combust all of the fuel that isdelivered into the cylinders of those engines and consequently emitfairly high levels of undesirable exhaust emissions. This is problematicparticularly as there continues to be increasing concern overenvironmental pollution, and various governmental entities arecontinuing to enact legislation and regulations tending to require thatsuch engine exhaust emissions be restricted to various levels. Suchcrankshaft-based engines also still require starters and flywheelmechanisms to allow for starting and proper operation of the engines.

Although most conventional internal combustion engines employ apiston-driven crankshaft, other designs for internal combustion engineshave also been developed. It is known, for example, to construct anengine in which the linear motion of pistons is transformed intorotational motion at an engine output not by way of connecting rods anda crankshaft, but rather by way of utilizing the pistons to drivehydraulic fluid toward a hydraulic motor that rotates in response toreceiving such hydraulic fluid. Yet even this type of engine can sufferfrom some of the same types of limitations described above. Inparticular, such engines typically also are limited in their efficiency,and/or require additional components such as a starter and/or flywheelin order to allow the engine to begin running in a steady-state manner,and to continue running in such a manner.

For at least these reasons, it would be advantageous if an improvedinternal combustion engine could be developed that did not suffer fromone or more of the above-described limitations to as great a degree. Inparticular, it would be advantageous if, in at least some embodiments,such an improved internal combustion engine was capable of operating ina more fuel-efficient manner than some or all of the above-describedconventional engines. Further, it would be advantageous if, in at leastsome embodiments, such an improved internal combustion engine could bedesigned to operate in such a manner that one or more commonly-employedcomponents (e.g., a starter or a flywheel) were not needed.

SUMMARY OF THE INVENTION

The present inventor has recognized the desirability of an improvedinternal combustion engine having greater fuel-efficiency. The presentinventor has further recognized that engine efficiency can be enhancedin any one or more of a variety of manners including, for example, byincreasing the compression ratio (or alternatively, the “expansionratio”) of an engine, by reducing engine fuel consumption when outputpower is not needed (e.g., when a vehicle is standing still), amongothers. The present inventor has additionally recognized thedisadvantages associated with the use of various components of manyconventional engines including, for example, crankshafts and associatedcomponents (e.g., connecting rods designed to link to crankshafts),camshafts and associated valve-train components (including, for example,timing chains, rocker arms, etc.), starters, flywheels, and variousother engine components commonly employed in conventional internalcombustion engines.

With one or more of these considerations in mind, the present inventorhas conceived of a new engine design that employs one or more pairs ofcylinders having oppositely-directed pistons that, in response tocombustion events, drive hydraulic fluid toward a hydraulic motor,thereby converting linear piston motional energy into rotational energy.In contrast to conventional engines, rather than employing pistonmovement in the form of compression strokes to achieve compressed air asis required for the combustion process, in such embodimentspre-compressed air is instead supplied to the cylinders from a sourceoutside of the cylinders. Consequently, in such embodiments, the engineis a two stroke engine in which only combustion strokes and exhauststrokes are performed by the pistons.

Further with respect to such embodiments, by physically linking thepistons of each pair to form an overall piston assembly, andappropriately controlling the provision of compressed air and fuel intothe piston cylinders and the combustion events within those cylinders,every movement of the pistons of each pair is a powered movement causedby a combustion event in one of those pistons. Thus, in such an enginedesign, each piston assembly is always in a state where it is possibleto perform a new combustion event. For this reason, such engines have noneed for any starter to initially power the engine, nor any flywheel toguarantee that the engine continues to advance to successive positionsat which combustion events can occur. Rather, such engines can berepeatedly turned on and off without any involvement by any starter orany flywheel.

As a result of such characteristics, improved engines in accordance withsuch embodiments are able to achieve higher fuel efficiencies on any oneor more of several counts. To begin with, such engines need not have anystarter and/or flywheel, and consequently can be lighter than manyconventional engines. Further, because the engines can be turned on andoff repeatedly without any involvement by any starter and/or flywheel,the engines need not remain running when output power is not needed(e.g., when a vehicle within which the engine is operating is stopped ata stop light). Also, because of the particular piston arrangement, andparticularly because the engines do not require any compression strokesinvolving the compression of fuel/air mixtures that could involvespontaneous pre-ignition, greater compression ratios (or “expansionratios”) and correspondent fuel efficiency improvements are possible.Additionally, because compression strokes are not ever performed withinthe piston cylinders, no corresponding loss of rotational momentum andenergy occurs as a result of such strokes.

More particularly, in at least some embodiments, the present inventionrelates to an internal combustion engine. The engine includes first andsecond cylinders having first and second hydraulic chambers,respectively, first and second combustion chambers, respectively, andfirst and second intake valves, respectively, the intake valves beingcapable of governing flow into the respective combustion chambers. Theengine further includes first and second pistons positioned within thefirst and second cylinders, respectively, the first and second pistonsbeing rigidly coupled to one another in a manner such that the pistonsare substantially aligned with one another and oppositely-directedrelative to one another. The engine additionally includes at least onehydraulic link at least indirectly connecting the first and secondhydraulic chambers with a hydraulic motor so as to convey hydraulicfluid driven from the first and second hydraulic chambers by the firstand second pistons to the hydraulic motor. The engine also includes atleast one source of compressed air that is linked at least indirectly tothe first and second combustion chambers by way of the respective intakevalves, the compressed air being provided to the combustion chambers inanticipation of combustion strokes whereby, due to the providing of thecompressed air from the at least one source, the first and secondpistons need not perform any compression strokes in order for combustionevents to occur therewithin.

Further, in at least some embodiments, the present invention relates toan internal combustion engine. The engine includes a first pistonprovided within a first cylinder, wherein a first combustion chamber isdefined within the cylinder at least in part by a face of the piston,and a first intake valve within the first cylinder capable of allowingaccess to the first combustion chamber. The engine further includes asource of compressed air, where the source is external of the firstcylinder and is coupled to the cylinder by way of the first intakevalve, and where the first piston does not ever operate so as tocompress therewithin an amount of uncombusted fuel/air mixture, wherebythe engine is capable of operating without a starter.

Additionally, in at least some embodiments, the present inventionrelates to a method in an internal combustion engine. The methodincludes (a) providing a cylinder assembly having first and secondcylinders and a piston assembly including first and second pistons thatare coupled to one another by rigid structure and positioned within thefirst and second cylinders, respectively, where inner and outer chambersare formed within each of the first and second cylinders, the innerchambers being positioned inwardly of the respective pistons along therigid structure and outer chambers being positioned outwardly of therespective pistons relative to the inner chambers, and wherein the innerchambers are configured to receive hydraulic fluid while the outerchambers are configured to receive amounts of fuel and air. The methodfurther includes (b) causing a first exhaust valve associated with theouter chamber of the first cylinder to close and a second exhaust valveassociated with the outer chamber of the second cylinder to open. Themethod additionally includes (c) opening a first intake valve associatedwith the outer chamber of the first cylinder to open, and (d) providingcompressed air along with fuel into the outer chamber of the firstcylinder upon the opening of the first intake valve. The method alsoincludes (e) closing the first intake valve, and (f) causing acombustion event to occur within the outer chamber of the firstcylinder, the combustion event tending to drive the piston assembly in amanner tending to expand the outer chamber of the first cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of an exemplary vehicle within which canbe implemented a hydraulic engine in accordance with at least oneembodiment of the present invention;

FIG. 2 is a schematic diagram of a hydraulic engine in accordance withat least one embodiment of the present invention, as can be employed inthe vehicle of FIG. 1;

FIG. 3 is a schematic diagram showing in more detail several of thecomponents of the hydraulic engine of FIG. 2, particularly severalinterrelated hydraulic and physical links among cylinders/pistons of thehydraulic engine;

FIG. 4 is a cross-sectional view of an assembly including a pair ofoppositely-oriented cylinders, a pair of interconnected pistons that arecapable of movement within those cylinders and associated hydraulicvalves, as can be employed within the hydraulic engine of FIGS. 2-3;

FIG. 5A is a partially cross-sectional, partially cut away sideelevation view of certain portions of the assembly of FIG. 4, withparticular components of the assembly shown in more detail than in FIG.4;

FIG. 5B is a partially cross-sectional, partially cut away (andpartially schematic) side elevation view of portions of one of thecylinders shown in FIG. 4 (including the piston positioned therein),particularly an exemplary cylinder head and certain componentsassociated with the cylinder head including a pressurized inductionmodule, intake and exhaust valves, and a fuel injector (such as areshown in FIG. 2), as well as additional components employed to actuatethe valves;

FIGS. 6A-6D respectively show in simplified schematic form an assemblyincluding a pair of oppositely-oriented cylinders, a pair ofinterconnected pistons that are capable of movement within thosecylinders and associated hydraulic valves and other components, as canbe employed within the hydraulic engine of FIGS. 2-5B, where some ofthose components are shown to be in first, second, third and forthpositions, respectively;

FIG. 7 is a flow chart illustrating a sequence of steps performed bycomponents of the hydraulic engine of FIGS. 2-3 in moving theinterconnected pistons of FIG. 6A-6D to and from the positions shown inthose figures;

FIGS. 8-11 are timing diagrams illustrating four different manners ofoperation of the hydraulic engine of FIG. 2 in terms of influencing thepositioning of a pair of interconnected pistons such as those of FIG. 4and FIGS. 6A-6D;

FIG. 12 is a schematic diagram illustrating exemplary interconnectionsamong electronic control circuitry and various components of the engineof FIGS. 2-6D;

FIG. 13 is a flow chart showing exemplary steps of operation of theelectronic control circuitry in monitoring and controlling variouscomponents of the engine of FIGS. 2-6D; and

FIG. 14 is a schematic diagram showing in more detail several componentsof an alternate embodiment of the hydraulic engine of FIG. 2 in whichthe engine includes a regenerative braking capability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an exemplary vehicle 2 is shown, within which canbe implemented an engine 4 (shown in phantom) in accordance with oneexemplary embodiment of the present invention. The vehicle 2 of FIG. 1,in particular, is shown to be an automobile capable of carrying one ormore persons, including a driver, and having four wheels/tires 6 thatsupport the vehicle relative to a road or other surface upon which thevehicle drives. Although FIG. 1 shows one exemplary vehicle, it shouldbe understood that the present invention is applicable to a wide varietyof different types of vehicles (e.g., automobiles, cars, trucks,motorcycles, all-terrain vehicles (ATVs), utility vehicles, boats,airplanes, hydrocraft, construction vehicles, farm vehicles, rideablelawnmowers, etc.), as well as other devices that do not necessarilytransport people (e.g., walk-behind lawnmowers, snowblowers, pumpingequipment, generators, etc.) that require or operate using one or moreengines that operate based upon one or more different types ofcombustible fuels, such as gasoline, diesel fuel, biofuels, hydrogenfuel, and a variety of other types of fuel. Indeed, the presentinvention is generally applicable to internal combustion enginesgenerally, regardless of whether they are implemented in vehicles andregardless of the purpose(s) for which the engines are used.

Turning to FIG. 2, various components of the engine 4 are shown inschematic form. As will be described in further detail below, the engine4 has a design that is primarily (albeit not entirely) hydraulic innature. More particularly as shown, the engine 4 in its presentembodiment includes a first set of piston cylinders 8 that includesfirst, second, third and fourth cylinders 10, 12, 14 and 16,respectively. As will be described further below with respect to FIG. 3,the cylinders of the first set 8 are coupled physically with oneanother, as well as coupled hydraulically with one another and with ahydraulic wheel motor 18, as represented figuratively by way of links20. Based upon power communicated hydraulically from the cylinders tothe hydraulic wheel motor 18, the hydraulic wheel motor 18 is able todirectly cause movement of one or possibly more than one of thewheels/tires 6 of the vehicle 2 or, in alternate embodiments notinvolving a vehicle, to otherwise output rotational power.

Further as shown, each of the cylinders 10, 12, 14 and 16 includes arespective combustion chamber 22 that interfaces several additionalcomponents. More particularly, each of the respective combustionchambers 22 interfaces a respective sparking device 24 that is capableof being controlled to provide sparks to the combustion chamber. Also,each of the respective combustion chambers 22 interfaces both arespective intake valve 26 and a respective exhaust valve 28. Eachrespective intake valve 26 is further coupled to a respectivepressurized induction module 30, which in turn is also coupled to arespective fuel injector 32. As will be described further below, thesparking devices 24, intake and exhaust valves 26 and 28, inductionmodules 30 and fuel injectors 32 are typically mounted within a headportion of the cylinder. The intake and exhaust valves 26, 28 in thepresent embodiment are electronically-controlled, pneumatic solenoidvalves and can, depending upon the embodiment, more particularly bea-way, normally-open, solenoid valves or 4-way valves. The components8-32 can generally be considered to constitute a core or main portion ofthe engine 4, as represented by a dashed line box 34.

As described further below with respect to FIG. 12, and as illustratedfiguratively in FIG. 2, the engine 4 also includes electronic controlcircuitry 116 that governs the timing of operations of the various fuelinjectors 32, intake valves 26, exhaust valves 28, and sparking devices24. The electronic control circuitry 116 can take a variety of formsdepending upon the embodiment including, for example, one or moreelectronic controllers or control devices such as microprocessors, orvarious other control device devices such as programmable logic devices(PLDs), or even discrete logic devices and/or hardwired circuitry. Asillustrated more clearly in FIG. 12, the electronic control circuitry116 is in communication with the fuel injectors 32, valves 26, 28 andsparking devices 24 (as well as additional components) by way ofdedicated wired links or possibly other communication links (e.g.,wireless communication links), by which the electronic control circuitryis able to provide control signals to those components and/or receivesignals from those components that can be used for monitoring purposesor otherwise. In at least some embodiments, it is even possible that theelectronic control circuitry 116 will be located remotely from theremainder of the engine 4 and be in communication therewith by way of awireless or even (particularly if the engine is stationary) wirednetwork, including possibly an internet-type network.

During engine operation, as controlled by the electronic controlcircuitry 116, the pressurized induction modules 30 receive fuel fromtheir respective fuel injectors 32 (which are located so as to directfuel into the air induction modules directly behind the intake valves)and also receive pressurized air, as described further below. The fuelinjection pulses can vary in their lengths, for example, from about 1-2ms pulses to up to 25 ms pulses (the fuel injection pulses typicallybeing at a higher pressure than the compressed air pressure). In turn,the respective intake valves 26 associated with the respectivepressurized induction module 30 are controlled to allow the resultingfuel/air mixture to proceed into the respective combustion chambers 22of the respective cylinders 10, 12, 14 and 16. Combustion events occurwithin the combustion chambers 22, in particular, after such fuel/airmixture has been added to the combustion chambers upon the occurrence ofsparks from the respective sparking devices 24 (there is little or nopossibility of pre-ignition prior to the sparking events). Thecombustion events taking place within the combustion chambers 22 causemovements of pistons within the piston cylinders 10, 12, 14 and 16,which in turn (due to the hydraulic/physical links 20) result inhydraulic power being communicated to the hydraulic wheel motor 18.Subsequent to the occurrences of the combustion events in the respectivecylinders 10-16, exhaust gases exit the respective combustion chambers22 by way of the respective exhaust valves 28, which also are controlledby the electronic control circuitry 116.

Still referring to FIG. 2, in addition to the components of the mainportion 34 of the engine 4, the engine includes other components aswell. Several of these components govern the provision of pressurizedair to the pressurized induction modules 30, as well as the provision offuel to the fuel injectors 32. Among these components are an air tank 36(which in the present embodiment is a half gallon air tank), a main aircompressor 38, an electric air compressor 40, a battery 42 (which canbe, for example, a 12 volt battery, or possibly a higher voltage batterysuch as a 24 volt battery), an auxiliary power unit 44, and anair-powered fuel pump 54 (alternatively, a fuel pump that is batterydriven or hydraulically driven can also be used). As shown, the air tank36 is coupled to each of the main air compressor 38 and the electric aircompressor 40, each of which can determine air pressure within the airtank (albeit the electric air compressor typically is only used in rarecircumstances when the main air compressor is unable to operate). Themain air compressor 38 is coupled to and powered by the auxiliary powerunit 44, while the electric air compressor 40 is coupled to and poweredby the battery 42. Depending upon the embodiment, the auxiliary powerunit 44 (by way of a generator) also can charge the battery 42 and/oroperate an air conditioning system of the vehicle 2, and/or provideelectrical power to any of a variety of other electrically-operatedcomponents/systems of the vehicle (e.g., a radio, power-adjustableseats, power-adjustable windows, etc.).

The auxiliary power unit 44 includes an auxiliary power unit hydraulicmotor/flywheel 46 and a second set of cylinders 48 that includes firstand second additional cylinders 50 and 52, respectively. The cylinders50 and 52 are coupled physically with one another, as well as coupledhydraulically with one another and with the auxiliary power unithydraulic motor/flywheel 46, as represented figuratively by links 57. Aswas the case with each of the cylinders of the first set 8, each of theadditional cylinders 50 and 52 includes a respective combustion chamber22 that is in communication with each of a respective sparking device24, a respective intake valve 26, and a respective exhaust valve 28.Further, each of the respective intake valves 26 of the respectivecylinders 50 and 52 is coupled to a respective pressurized inductionmodule 30, which in turn is coupled to a respective fuel injector 32.Again, each of the fuel injectors 32, valves 24, 26 and sparking devices28 are controlled by the electronic control circuitry 116.

Additionally as shown, the pressurized induction modules 30 associatedwith each of the cylinders of the first and second sets of cylinders 8,48 are provided with pressurized air from the air tank 36 by way oflinks 56. Further, the air powered fuel pump 54 also receives, and isdriven by, pressurized air from the air tank 36 by way of the links 56.In response to receiving the pressurized air, the fuel pump 54 in turnsupplies pressurized fuel to the fuel injectors 32 of each of thecylinders of the first and second sets of cylinders 8, 48, by way ofadditional links 58.

During normal operation of the engine 4, compression events occur withinthe cylinders 50, 52 of the auxiliary power unit 44 and, as a result,pistons within the cylinders 50, 52 move. Due to the movement of thepistons within the cylinders 50 and 52, hydraulic fluid is communicatedthrough, and thereby causes rotation of, the auxiliary power unithydraulic motor/flywheel 46, which in turn operates the air compressor38 and thus generates pressurized air within the air tank 36. Thepressurized air is communicated to the air powered fuel pump 54 as wellas to each of the pressurized induction modules 30 associated with eachof the cylinders of the first and second sets 8, 48 by way of the links56, allowing for combustion events to occur within each of thosecylinders. Additionally, even when the auxiliary power unit 44 is notexperiencing combustion events, pressurized air can still (occasionallywhen appropriate) be generated within the air tank 36 and thuscommunicated to the pressurized induction modules 30 and air poweredfuel pump 54, due to the operation of the electric air compressor 40 andthe battery 42.

As indicated by the links 20 and 57 discussed above, the cylinders ofthe first and second sets 8, 48 within the engine 4 are hydraulicallycoupled to the hydraulic wheel motor 18 and the auxiliary power unithydraulic motor/flywheel 46, respectively. Thus, in contrast to manyconventional internal combustion engines, the engine 4 employs cylinders(and pistons therewithin) not to provide rotational torque to acrankshaft that in turn provides rotational output power, but rather tomove hydraulic fluid through the links 20, 57 to the hydraulic wheelmotor 18 and the auxiliary power unit hydraulic motor/flywheel 46 so asto generate rotational output power. That is, the flow of the hydraulicfluid causes rotational movement (and thus vehicle movement). Flow ofthe hydraulic fluid also is accompanied by pressure, where the amount ofpressure is typically a function of the resistance to the flow by theload (the flow of hydraulic fluid provided by the engine is somewhatanalogous to current provided by a current generator in an electriccircuit, while the pressure resulting from the flow is analogous to avoltage that is created due to the resistance to that current flowarising from the load). Insofar as the pistons within the cylinders ofthe first and second sets 8, 48 are not tied to any crankshaft, thosepistons can be considered “free pistons” having sliding motion that isnot constrained by any such crankshaft.

Additionally, as will be described in further detail below with respectto FIGS. 6A-11, in contrast to many conventional engines in whichcylinders operate in a 4 stroke (or 4 cycle) manner involving intake,compression, combustion and exhaust strokes, the cylinders of the firstand second sets 8, 48 of the engine 4 instead are operated merely in a 2stroke manner. More particularly, the cylinders of the first and secondsets 8, 48 each are operated so as to only experience combustion strokesand exhaust strokes. It is just prior to the combustion strokes thatfuel and air are forced into the combustion chambers 22 of the cylindersby way of the respective intake valves 26. No compression strokes needbe performed by the cylinders in the present embodiment, since thecombustion chambers 22 receive precompressed air directly from thepressurized induction modules 30. Also, in contrast to a 4 strokeengine, the input of fuel/air into the combustion chambers 22 is notperformed during any strokes of the engine but rather occurs almostinstantaneously prior to the combustion strokes.

Further with respect to the manner in which fuel and air is providedinto the combustion chambers 22, it should be mentioned that it isgenerally desirable to maintain a substantially (or entirely) constantfuel-to-air ratio in the combustion chambers at all engine speeds (e.g.,a 14.7 to 1 ratio of fuel to air by weight). Becauseelectronically-controlled, pneumatic solenoid valves are used to actuatethe intake valves 26, it can be assumed that varying the duration of theintake valve pulse (in conjunction with varying the duration of the fuelinjection pulse) would be the most appropriate method for controllingthe induction process. Such a method can be achieved through the use ofintake valves that are 4-way, two position solenoid valves.

While such an implementation can be employed in some embodiments,through testing, it has been determined that it often is difficult tolinearly control the induction when actuating the above-describedsolenoid valves in such a manner. More particularly, in testing it hasbeen determined that the solenoid valves often take approximately 9 msto begin to actuate, but if the valves are actuated for 12 ms or longer,the maximum charge of air will be swept into the combustion chamber.That is, due to the use of pressurized air from the air tank 36, airenters the combustion chambers 22 rapidly when the intake valves 26 areopened and, when the intake valves begin to open, the fuel/air mixtureenters with such force and speed that it can sometimes be difficult toregulate the amount of the fuel/air mixture (and particularly the amountof air) that enters the combustion chamber.

As an alternative, through testing it has been found that the use of4-way valves can allow for more positive control if controlled in aparticular manner. The extra output port available in a 4-way valve canbe used to pressurize a rear intake plunger chamber of the valve whenthe solenoid is energized, such that the vent hole used to vent thatchamber can be (and must be) eliminated. When the solenoid isde-energized, the chamber is vented through the internal porting of the4-way valve itself. Using such a valve, it has further been demonstratedthat, in order to better regulate the amount of air (and fuel) enteringthe combustion chamber via such a valve, the intake valve should beactuated to open for a predetermined constant length of time (e.g., 12ms) and to regulate the amount of air by varying the pressure of theinduction air. The amount of fuel that is injected can still becontrolled by varying the duration of the fuel injector pulse.

Although some embodiments of the present invention envision the use of apressurized air supply such as the air tank 36 having a constantpressure (for example, at 150 to 175 psi), in other embodiments,regulation of the pressure of the induction air can be attained byvarying the pressure at the air tank 36. In such embodiments, thepressure within the air tank 36 can be varied by controlling the mainair compressor 38 (or the electric air compressor 40) in real time basedupon various criteria, such as the degree to which an operator hasdepressed an accelerator pedal (as shown in FIG. 12). Given such anarrangement, when an accelerator pedal is lightly depressed, the airpressure within the air tank 36 can be regulated and maintained at alower pressure (e.g., 40 psi) while, when the accelerator is depressedmore fully, the air pressure can be regulated and maintained at a higherpressure (e.g., 160 psi), with the regulated pressure having anapproximately linear relation to the amount of accelerator depression.Such an implementation involving varying air pressure is likely to becomparatively fuel-efficient, as energy need not be wasted incompressing induction air to a pressure higher than that needed forcombustion.

Turning to FIG. 3, a further schematic diagram 60 shows in more detailthe cylinders 10-16 and the hydraulic wheel motor 18 of the main portion34 and the interrelationship among those components physically andhydraulically, as represented figuratively by the links 20 of FIG. 2. Asshown, each of the cylinders 10-16, in addition to having its respectivecombustion chamber 22, also includes a respective hydraulic chamber 64and a respective piston 62 separating the combustion and hydraulicchambers from one another. In the present embodiment, the first andsecond cylinders 10 and 12 are arranged coaxially, and likewise thethird and fourth cylinders 14 and 16 are arranged coaxially. The pistons62 of the first and second cylinders 10 and 12 are rigidly coupled toone another by a first piston connector tube 66, while the pistons ofthe third and fourth cylinders 14, 16 are rigidly connected to oneanother by way of a second piston connector tube 68. The two connectortubes 66, 68 are parallel (or substantially parallel) to one another andspaced apart such that the first cylinder 10 is adjacent to the thirdcylinder 14 and the second cylinder 12 is adjacent to the fourthcylinder 16. Although the present arrangement of the connector tubes 66,68 in this manner is advantageous for engine balancing purposes, otherarrangements can be employed that are equally (or substantially equally)beneficial for engine balancing including, for example, an X-shapedarrangement in which the axis of the first and second cylinders isperpendicular to the axis of third and fourth cylinders.

Further as shown, the first and second cylinders 10, 12 are arranged inan opposed manner such that the first piston connector tube 66 extendsbetween the respective pistons 62 of the cylinders, the hydraulicchambers 64 of the respective cylinders are each positioned inwardly ofthe respective pistons within the cylinders along the connector tube,and the combustion chambers 22 of the respective cylinders are eachpositioned outwardly of the respective pistons within the cylinders.Likewise, the first and second cylinders 14, 16 are arranged in anopposed manner such that the second piston connector tube 68 extendsbetween the respective pistons 62 of the cylinders, such that thehydraulic chambers 64 of the respective cylinders are each positionedinwardly of the respective pistons within the cylinders along theconnector tube, and such that the combustion chambers 22 of therespective cylinders are each positioned outwardly of the respectivepistons within the cylinders.

Given this arrangement, movement of the pistons 62 of the first andsecond cylinders 10, 12 are coordinated with one another, and themovements of the pistons of the third and fourth cylinders 14, 16 arecoordinated with one another. However, because the cylinders 10 and 12are oriented in the opposed, back-to-back manner, movement of theconnector tube 66 with the pistons 62 of those cylinders in onedirection tends to reduce the size (volume) of the combustion chamber 22of one of the cylinders while expanding the combustion chamber of theother of those two cylinders, and movement of the connector tube andthose pistons in the opposite direction tends to have the oppositeeffects on the respective combustion chambers of those cylinders.Likewise, movement of the connector tube 68 along with the pistons 62 ofthe third and fourth cylinders 14, 16 in one direction tends to reducethe size of one of the combustion chambers 22 of one of those cylinderswhile expanding the size of the other of the combustion chambers ofthose cylinders, while movement of the connector tube and those pistonsin the opposite direction tends to have the opposite effects on therespective combustion chambers of those cylinders. It should further benoted that, when the combustion chambers 22 are expanding due tocombustion events within those chambers, those chambers can be thoughtof as expansion chambers due to the adiabatic expansions that areoccurring therein. In contrast, when the combustion chambers 22 arecontracting (e.g., in response to combustion events that are occurringwithin others of the combustion chambers), those chambers can be thoughtas exhaust chambers, since at such times the exhaust valves 28associated with those chambers are opened to allow the contents of thosechambers to exit those chambers.

Additionally, as the connector tube 66 and its respective pair ofpistons 62 move in a given direction so as to affect the sizes (volumes)of the combustion chambers of the cylinders 10 and 12, complementarychanges in the sizes (volumes) of the respective hydraulic chambers 64of those cylinders also occur. For example, as the connector tube 66 andits pistons 62 move in one direction, this tends to reduce the size ofthe hydraulic chamber 64 of one of the cylinders that is alsoexperiencing an increase in the size of its combustion chamber 22, andtends to increase the size of the hydraulic chamber of the other of thecylinders that is simultaneously experiencing a reduction in the size ofits combustion chamber. Likewise, as the connector tube 68 and itsrespective pair of pistons 62 move in a given direction so as to affectthe sizes of the combustion chambers of the cylinders 14 and 16,complementary changes in the sizes of the respective hydraulic chambers64 of those cylinders also occur.

For example, in the present view shown in FIG. 3, the connector tube 66and corresponding pistons 62 of the first and second cylinders 10, 12are shown to be in a substantially leftward position as indicated by anarrow 71. Given this to be the case, the combustion chamber 22 of thefirst cylinder 10 is smaller than the combustion chamber of the secondcylinder 12, while the hydraulic chamber 64 of the first cylinder islarger than the hydraulic chamber of the second cylinder 12. Incontrast, the connector tube 68 and corresponding pistons 62 of thethird and fourth cylinders 14, 16 are shown to be in a substantiallyrightward position as indicated by an arrow 73. Consequently, thecombustion chamber 22 of the third cylinder 14 is larger than thecombustion chamber of the fourth cylinder 16, while the hydraulicchamber 64 of the third cylinder is smaller than the hydraulic chamberof the fourth cylinder.

Actuation of the various cylinders 10-16 causes back and forth movementof the connector tubes 66 and 68 and their respective pistons 62 in thedirections represented by the arrows 71 and 73. In the presentembodiment, it is generally preferred that, for engine balancingpurposes, the connector tube 66 and its corresponding pistons 62 beoperated to move in a manner that is consistently the opposite of themovements of the connector tube 68 and its corresponding pistons 62, andvice-versa. That is, when the connector tube 66 and its correspondingpistons 62 are actuated to move along the direction indicated by thearrow 71, the connector tube 68 and its pistons are actuated to move inthe direction indicated by the arrow 73, and vice-versa. However, inalternate embodiments, such opposite, balanced movements of the pistons62 and connector tubes 66, 68 associated with the two pairs of cylinders10, 12 and 14, 16 need not occur, and rather the respective connectortubes and their corresponding pistons can move entirely independently ofone another (indeed, it is possible for the engine 4 to operate evenwhen the pistons 62 of only one of the pairs of cylinders 10, 12 and 14,16 are moving).

As indicated above, the links 20 of FIG. 2 are intended to berepresentative of not only physical links between the cylinders 10-16such as the connector tubes 66, 68, but also hydraulic links couplingthe cylinders with one another and with the hydraulic wheel motor 18. Inthis regard, FIG. 3 further shows how the hydraulic chambers 64 of thecylinders 10-16 are coupled with one another and with hydraulic wheelmotor 18 by way of multiple check valves that restrict the direction offluid flow into and out of the hydraulic chambers. More particularly asshown, hydraulic fluid is provided from a hydraulic reservoir 70 by wayof a link 94 to first and second check valves 72 and 74, respectively,which in turn are coupled to the hydraulic chambers 64 of the first andsecond cylinders 10 and 12, respectively. The check valves 72 and 74only allow hydraulic fluid to flow into the respective hydraulicchambers 64 and not out of those chambers. Consequently, when one of thehydraulic chambers 64 of the first and second cylinders 10 and 12 tendsto expand (e.g., during an exhaust stroke of that cylinder), thenhydraulic fluid is drawn into (but does not flow out of) that hydraulicchamber (e.g., due to suction) via a given one of the check valves 72and 74 that is associated with that chamber, but when that hydraulicchamber contracts (e.g., during a combustion stroke of that cylinder),then that given check valve prevents outflow of the hydraulic fluid backto the hydraulic reservoir 70.

In addition to the check valves 72 and 74, respectively, the respectivehydraulic chambers 64 of the respective first and second cylinders 10and 12 are also coupled to third and fourth check valves 76 and 78,respectively, which in turn are coupled to one another and also coupledto a link 80. The check valves 76 and 78 are respectively orientated toallow hydraulic fluid flow out of the respective hydraulic chambers 64of the first and second cylinders 10 and 12, respectively, to the link80, but not to allow backflow into those hydraulic chambers from thatlink. Further, fifth and sixth check valves 82 and 84, respectively,additionally couple the link 80 to the hydraulic chambers 64 of thethird and fourth cylinders 14 and 16, respectively. The check valves 82,84 are orientated to allow hydraulic fluid flow to proceed from the link80 into the hydraulic chambers 64 of the cylinders 14, 16, but topreclude hydraulic fluid flow from those chambers back to that link.

Given the configuration of the check valves 76, 78, 82 and 84 and thelink 80, when one of the hydraulic chambers 64 of the first and secondcylinders 10 and 12 contracts, fluid flow proceeds from that contractingchamber by way of its respective one of the check valves 76, 78 throughthe link 80 to the check valves 82 and 84, by which the fluid is in turnable to enter the hydraulic chambers 64 of the third and fourthcylinders 14, 16. Typically, hydraulic fluid tends to flow into one(rather than both) of the hydraulic chambers 64 of a given pair ofcylinders of a cylinder assembly that is expanding due to movement ofthe pistons 62 within those cylinders. It is additionally possible forhydraulic fluid to pass, via the check valves 72, 74, 76, 78, 82 and 84,from the reservoir 70 into the hydraulic chambers 64 of the cylinders14, 16 even when the pistons 62 within the cylinders 10, 12 are notmoving.

Finally, seventh and eighth check valves 86 and 88, respectively, areadditionally coupled between the hydraulic chambers 64 of the third andfourth cylinders 14 and 16, respectively, and a link 90. The seventh andeighth check valves 86, 88 are both orientated to allow outflow ofhydraulic fluid from the hydraulic chambers 64 of the cylinders 14, 16to the link 90, and to preclude backflow from that link into thosechambers. The link 90 as shown further couples the check valves 86, 88to the hydraulic wheel motor 18, which in turn is coupled back to thehydraulic reservoir 70 by way of a link 92. Thus, hydraulic fluidflowing out of the hydraulic chambers 64 of the cylinders 14, 16 isdirected to and powers the hydraulic wheel motor 18 and, after passingthrough that motor, then returns to the hydraulic reservoir 70.

Given the presently-described arrangement of the cylinders 10-16,pistons 62, connector tubes 66, 68, check valves 72-78 and 82-88, andlinks 80 and 90-94, the movement of one or both of the coupled pairs ofpistons within the pairs of cylinders 10, 12 and 14, 16 causes hydraulicfluid flow to occur from the reservoir 70 through one or both of thehydraulic chambers 64 of one or both of the cylinders 10, 12 (the lowerpressure pair of cylinders), then subsequently through one or both ofthe hydraulic chambers of the third and fourth cylinders 14, 16 (thehigher pressure pair of cylinders) and ultimately to the hydraulic wheelmotor 18, which then directs the hydraulic fluid back to the reservoir70. During normal operation, when both the pistons 62 and connector tube66 of the cylinders 10, 12 and the pistons and connector tube 68 of thecylinders 14, 16 are experiencing movement, hydraulic fluid inparticular flows from the reservoir 70 through that one of the hydraulicchambers 64 of the cylinders 10, 12 that is expanding, then through thatone of the hydraulic chambers of the cylinders 14, 16 that is expanding,and then to the hydraulic wheel motor 18 (and further back to thereservoir). Hydraulic fluid flow through the hydraulic chambers 64 ofthe cylinders occurs regardless of the particular motion of the pistons62 and connector tubes 66, 68. That is, any movement tending to contractany one or more of the hydraulic chambers 64 tends to force hydraulicfluid to move through the system, even if the movement only relates tothe pistons 62 and connector tube 66 or 68 of one of the pairs ofcylinders 10, 12 and 14, 16.

In addition, simultaneous movements involving both of the connectortubes 66, 68 and all of the pistons 62 of all of the cylinders 10-16tend to be additive. That is, equal movements occurring with respect toboth of the pairs of cylinders 10, 12 and 14, 16 tend to produce doublethe effective hydraulic fluid pressure available to the hydraulic wheelmotor 18 as would otherwise occur with movement occurring with respectto only one of the pairs of cylinders. Further, such hydraulic fluidflow occurring in response to movement with respect to both of the pairsof cylinders 10, 12 and 14, 16 occurs regardless of whether the pistons62 and connector tube 66 of the first and second cylinders 10, 12 aremoving in the same or opposite direction as the pistons 62 and connectortube 68 of the third and fourth cylinders 14, 16. Nevertheless, asmentioned above, engine balancing is best achieved when the pistons 62and connector tube 66 of the first and second cylinders 10, 12 move in adirection that is opposite to the movement of the pistons and connectortube 68 of the third and fourth cylinders 14, 16.

Although a schematic diagram similar to that of FIG. 3 is not providedregarding the cylinders 50, 52, auxiliary power unit hydraulicmotor/flywheel 46 and links 57 of the auxiliary power unit 44 to show inmore detail the physical and hydraulic interrelationships among thosecomponents, it will nonetheless be understood that those componentsinteract in a manner similar to that shown in FIG. 3. More particularly,the cylinders 50 and 52 like the cylinders 10 and 12 of FIG. 3 haverespective pistons that are coupled by a respective connector tubelinking those pistons, such that movement of the two pistons iscoordinated. Further, each of the cylinders 50 and 52 includes, inaddition to its respective combustion chamber 22, a respective hydraulicchamber corresponding to the hydraulic chambers 64 of the pistons 10 and12 of FIG. 3. The cylinders 50, 52 again are arranged in an opposedmanner such that, when one of the pistons of those cylinders 50, 52moves in a direction tending to increase the size of the combustionchamber 22 of that cylinder, the hydraulic chamber of that cylindertends to be reduced in size while the combustion chamber of the oppositecylinder tends to decrease in size and the hydraulic chamber of thatopposite cylinder tends to increase in size.

Additionally, since the auxiliary power unit 44 includes only the twocylinders 50, 52, the auxiliary power unit only includes four checkvalves. First and second of the four check valves correspond to thecheck valves 72 and 74 of FIG. 3 and allow hydraulic fluid flow toproceed, by way of a link (not shown), only from a hydraulic reservoir(not shown) into the respective hydraulic chambers of the cylinders 50and 52. Additionally, third and fourth of the four check valvescorrespond to the check valves 86 and 88 of FIG. 3 and only allowhydraulic fluid flow to proceed from the respective hydraulic chambersof the cylinders 50 and 52, by way of another link (not shown), to theauxiliary power unit hydraulic motor/flywheel 46, which in turn iscoupled to the hydraulic reservoir. Typically, the hydraulic reservoirproviding hydraulic fluid to the cylinders 50 and 52 of the auxiliarypower unit 44 is the same hydraulic reservoir 70 as is used with thecomponents of the main portion 34 of the engine 4.

In alternate embodiments, neither the main portion 34 of the engine 4nor the engine's auxiliary power unit 44 need have the particularnumbers of cylinders and pistons shown in FIGS. 2 and 3 and/or otherwisedescribed above. For example, in some alternate embodiments, just as theauxiliary power unit 44 is capable of operating through the use of onlya single pair of oppositely-orientated cylinders 50 and 52, the mainportion 34 can similarly employ only a single pair ofoppositely-orientated cylinders rather than the set of four cylindersshown. Further, in some alternate embodiments, the auxiliary power unit44 can likewise have two pairs of cylinders as does the main portion 34.Additionally, in some alternate embodiments, one or both of the mainportion 34 of the engine 4 and the auxiliary power unit 44 can have morethan two pairs of oppositely-orientated cylinders. For example, the mainportion 34 can employ four pairs of cylinders. Such an embodiment canprovide enhanced balancing to the extent that the pistons of the twoinnermost pairs of cylinders are driven to move in a direction oppositeto the movements of the pistons of the two outermost pairs of cylinders.Also, in at least some embodiments, no auxiliary power unit is needed atall, for example, if there is an alternate source of pressurized air.

Although it is possible that in some alternate embodiments there will beone or more cylinders with pistons that are not coupled respectively tooppositely-orientated pistons (e.g., by way of connector tube(s)), suchembodiments are not preferred. By employing oppositely-orientated,coupled pairs of pistons as described above, movement of a given pistondue to a combustion event can be readily controlled and limited byactuation of (e.g., by causing a combustion event at) the other,oppositely-orientated piston that is coupled to the given piston, or atleast controlled and limited by the physical confines of the cylindersand other associated components, some of which are described furtherbelow in more detail with respect to FIGS. 4 and 5A. Relatedly, byemploying oppositely-orientated, coupled pairs of pistons, a givenpiston experiencing a combustion event can often be easily returned toits initial position prior to the combustion event by actuating theother, oppositely-orientated piston to which the given piston iscoupled.

While FIGS. 2-3 show components of the engine 4 in schematic form, FIG.4 in contrast shows an exemplary cross-sectional view of a cylinderassembly 100 including a pair of interconnected cylinders of thatengine, along with associated components. More particularly, FIG. 4shows the cylinders 10, 12 and associated components of FIGS. 2 and 3,including the connector tube 66 linking the pistons 62 within thosecylinders and the check valves 72, 74, 76 and 78 associated with thosecylinders. The combination of the connector tube 66 and associatedpistons 62 in particular can be referred to as a piston assembly 67.Although intended to be representative of the cylinders 10, 12 andassociated components, FIG. 4 is equally representative of any of thepairs of oppositely-orientated cylinders and associated components ofthe engine 4 as described above with respect to FIGS. 2 and 3. Thus,FIG. 4 also is representative of the cylinders 14, 16, the connectortube 68, and the check valves 82, 84, 86 and 88 within the main portion34 of the engine 4, as well as the cylinders 50, 52 and associatedconnector tube and check valves of the auxiliary power unit 44 of theengine.

As described above and further shown in FIG. 4, each of the respectivecylinders 10, 12 has its respective combustion chamber 22 and itsrespective hydraulic chamber 64, where the two chambers of each cylinderare separated by its respective piston 62. The outer walls of each ofthe respective cylinders 10, 12 are formed by a main engine housing 102,respective cylinder heads 112 at opposite ends of the assembly 100, andrespective cylindrical sleeves 114 that are positioned between therespective cylinder heads and the main engine housing. Further as shown,in the present embodiment, each of the cylindrical sleeves 114 includesa respective mounting flange 113 by which the sleeve is specifically incontact with the main engine housing 102. The hydraulic chambers 64 ofthe two cylinders 10, 12 are separated from one another by way of acenter bulkhead 104 of the main engine housing 102. Although not shownin FIG. 4, it will be understood that the respective cylinder head 112of each cylinder 10, 12 has formed therewithin an intake valve such asthe intake valves 26 of FIG. 2, an exhaust valve such as the exhaustvalves 28 of FIG. 2, and a sparking device such as the sparking devices24 of FIG. 2. Also, the fuel injectors 32 and the pressurized inductionmodules 30 likewise are supported by the cylinder heads 112. Suchcomponents provided within the cylinder head 112 are shown in moredetail in FIG. 5B.

Further as shown in FIG. 4, the check valves 72, 74, 76 and 78 arerespectively connected to ports 96, 98, 124 and 126, respectively, eachof which is formed within the main engine housing 102. By virtue of therespective ports 96 and 98, the respective check valves 72 and 74 areconnected to the link 94 (see FIG. 3), and by virtue of the respectiveports 124 and 126, the respective check valves 76 and 78 are connectedto the link 80 (see FIG. 3). In such embodiments, the link 94 can be abranched (e.g., Y-shaped) hose coupled at one end to the reservoir 70and at its other two ends to the ports 96 and 98. Also, the link 80 canlikewise be a hose having two branches so as to connect to the ports 124and 126. Further, if alternatively FIG. 4 is understood to represent thecylinders 14, 16 and associated components, the ports within the mainengine housing 102 instead can link the check valves with the link 80and the link 90. Likewise, if alternatively FIG. 4 is understood torepresent the cylinders 50, 52 and associated components, the portswithin the main engine housing 102 instead can link check valvesassociated with those cylinders with links to the auxiliary power unithydraulic motor/flywheel 46 and hydraulic fluid reservoir in conjunctionwith which those cylinders are operated, as discussed above.

Notwithstanding the particular embodiment of FIG. 4, the components of acylinder assembly of the engine can take many other forms as well. Forexample, in some alternate embodiments, both of the check valves 72 and74 are linked internally to one another and to a single port (e.g.,either the port 96 or the port 98). Likewise, in some alternateembodiments, both of the check valves 76 and 78 are linked internally toone another and to a single port (e.g., either the port 124 or the port126). In such embodiments, the hose-type links that are coupled to theports of the cylinder assembly need not be branched. Indeed, in someembodiments, hose-type links can be largely or entirely dispensed with(and incorporated into a hydraulic manifold), to the extent that some orall of the links among the various check valves of the various cylinderassemblies and other check valves are formed within the main enginehousings 102 of the respective cylinder assemblies and adjacent enginestructures. For example, in one alternate embodiment, a portion 130 ofthe engine could be increased in terms of its volume and could serve asthe reservoir 70 of the engine 4.

When combustion events occur within the combustion chambers 22 of thecylinders 10, 12 shown in FIG. 4, the piston assembly 67 including theconnector tube 66 and associated pistons 62 moves back and forth along acentral axis 132. In the exemplary view of FIG. 4, the piston assembly67 has been shifted towards the cylinder 10 (and away from the cylinder12), which typically will be the case when the most recent combustionevent occurring within the pair of cylinders 10, 12 occurred within thecombustion chamber 22 of the cylinder 12. Although the piston assembly67 could potentially be restricted in terms of its overall side-to-sidemovement by the cylinder heads 112 (with the movements to either sidebeing constrained when the pistons physically encountered the cylinderheads), restriction of such movement by the cylinder heads would not bepreferable since the relatively large momentum of the piston assemblycould cause wear upon the cylinder heads and/or the pistons due to theimpacts between those structures. Also, while the piston assembly 67, asit moves toward a particular one of the combustion chambers 22 followinga combustion event, can be pneumatically braked due to compression ofany contents within that combustion chamber, such pneumatic braking istypically inadequate to slow and stop such movement of the pistonassembly 67.

Rather, in the present embodiment, the connector tube 66 is fitted witha pair of connector tube collars 134, where one of the connector tubecollars is positioned along the connector tube 66 within each of therespective cylinders 10 and 12, respectively. Additionally, the mainengine housing 102 includes a pair of dashpot assemblies 136 that, asshown, are located on opposite sides of the center bulkhead 104 at theinnermost ends of the hydraulic chambers 64, respectively. As will bedescribed in further detail with respect to FIG. 5A, the respectiveconnector tube collars 134 are capable of sliding inwardly into therespective dashpot assemblies 136 depending upon the position of thepiston assembly 67. In the present view shown, for example, theconnector tube collar 134 associated with the cylinder 12 has slid intothe dashpot assembly 136 associated with that cylinder due to themovement of the piston assembly 67 toward the cylinder 10.

Due to the presence of the connector tube collars 134 and the dashpotassemblies 136, movement of the piston assembly 67 typically isrestricted not by way of the cylinder heads 112, but rather due to theinterfacing of the connector tube collars with the dashpot assemblies(albeit, in some circumstances, movement of the piston assembly 67 canalso be limited due to restrictions on the flow of hydraulic fluid outof the hydraulic chambers 64, such as when there are large loads on theengine 4). Entry of each respective connector tube collar 134 into itsrespective dashpot assembly 136 results in a rapid slowing-down andstopping of movement of the respective connector tube collar toward thecenter bulkhead 104, and thus results in a rapid slowing-down andstopping of the movement of the piston assembly 67 in that direction.For example, entry of the connector tube collar 134 of the secondcylinder 12 into the respective dashpot assembly 136 of that cylinder asshown in FIG. 4 presumably resulted in the slowing and stopping ofmovement of the piston assembly 67 to the left. Additionally, due to theparticular configuration of the dashpot assemblies 136 and the connectortube collars 134, the manner in which these components interface oneanother allows for effective slowing-down and stopping of the movementof the piston assembly 67 without damaging impacts and correspondentwear upon those components or upon the cylinder heads 112 of thecylinders 10, 12.

Referring further to FIG. 5A, a partially cross-sectional, partially cutaway side elevation view of certain portions of the assembly 100 of FIG.4 reveals certain features of the assembly in more detail. Moreparticularly, FIG. 5A provides a side elevation view of a portion of thepiston assembly 67 within the cylinder 12, along with the dashpotassembly 136 associated with that cylinder. Additionally, FIG. 5Aprovides a cross-sectional view of a portion of the center bulkhead 104of the main engine housing 102 that surrounds the portion of the pistonassembly 67 extending therewithin. It will be understood that thefeatures shown in FIG. 5A with respect to the dashpot assembly 136associated with the cylinder 12 are equally present with respect to thedashpot assembly of the cylinder 10, as well as with respect to dashpotassemblies associated with each of the other cylinders 14, 16, 50 and 52of the engine 4 shown in FIG. 2. It will further be recognized that FIG.5A shows the piston assembly 67 to be in a somewhat different positionthan that shown in FIG. 4, such that the connector tube collar 134associated with the cylinder 12 is no longer positioned within thedashpot assembly 136 of that cylinder, but rather is shifted to theright of that dashpot assembly.

As shown in FIG. 5A, the dashpot assembly 136 includes severalsubstructures. First among these is a cylindrical capacitor case orsleeve 138 within which is formed a cylindrical cavity 140, having aninner diameter that is slightly greater than an outer diameter of theconnector tube collar 134 (e.g., by approximately eighteen thousandthsof an inch). Thus, as the piston assembly 67 moves in a directionillustrated by an arrow 143, the connector tube collar 134 associatedwith the cylinder 12 is able to slide into the cavity 140. Further asshown, the cylindrical capacitor case 138 is supported upon an oil sealcover 142 that in turn is supported upon the center bulkhead 104.Additionally, an annular oil seal 144, which can be an o-ring, ismounted along the interface between the dashpot assembly 136 and thecenter bulkhead 104, and can be considered to be part of the dashpotassembly. Further, although not shown, it will be understood thattypically one or more sealing rings (for example, metallic rings) aretypically mounted around the exterior cylindrical surface of the piston62, to prevent or limit leakage of hydraulic fluid from the hydraulicchamber 64 on one side of that piston to the combustion chamber 22 onthe other side of that piston (as well as to prevent or limit leakage offuel/air and combustion byproducts from the combustion chamber into thehydraulic chamber). In one embodiment, such sealing rings should limitthe amount of hydraulic fluid that is capable of leaking into thecombustion chamber 22 of the cylinder (from the opposite side of thepiston) to only about 0.05% by volume of the hydraulic fluid within thecylinder. A return mechanism can be provided within the combustionchamber allowing hydraulic fluid that has leaked into the combustionchamber to be returned to the reservoir 70.

The oil seal cover 142, like the capacitor case 138, is acylindrical/annular structure. However, the oil seal cover 142 has aninner diameter that is less than the inner diameter of the capacitorcase 138 and in particular is only about the same as (or slightlygreater than) the outer diameter of the connector tube 66, which isnarrower than the outer diameter of the connector tube collar 134.Consequently, while movement of the connector tube 66 is not preventedby the oil seal cover 142, the connector tube collar 134 is completelyprecluded from advancing past the oil seal cover farther toward thecenter bulkhead 104. Further, because of the relative sizes of the innerdiameter of the oil seal cover 142 and the outer diameter of theconnector tube 66, and also because of the sealing provided by the oilseal 144, the passage of hydraulic fluid from the hydraulic chamber 64of the cylinder 12 through the center bulkhead 104 to the oppositecylinder 10 is entirely or at least substantially precluded.

It should be further noted that the particular outer and inner diametersof the connector tube 66 and the oil seal cover 142, respectively, canvary depending upon the embodiment. Also, the connector tube 66 can varyin its diameter along its length. Often it is desirable to have thediameter of the connector tube 66 be fairly large, particularly near thepiston 62, such that its diameter is not much less than the outerdiameter of the piston. Through the use of such an arrangement, anypressure applied to the surface of the piston 62 facing the combustionchamber 22 during combustion is magnified or leveraged within thecorresponding hydraulic chamber 64, since the annular surface of thepiston facing the hydraulic chamber 24 is significantly smaller in areathan the surface of the piston facing the corresponding combustionchamber 22.

Although the connector tube collar 134 cannot pass beyond the oil sealcover 142, in practice the connector tube collar never (or seldom)reaches the oil seal cover due to the operation of the dashpot assembly136 in relation to the connector tube collar. More particularly asshown, the capacitor case 138 can be understood as encompassing a firstcylindrical portion 146 that is located farther from the center bulkhead104 and a second cylindrical portion 148 that is located closer to thecenter bulkhead. Further, the second cylindrical portion 148, as shown,includes one or more (in this case, four) dashpot orifices 150 extendingthrough the wall of the capacitor case 138. The dashpot orifices 150allow hydraulic fluid to exit the cavity 140 as the connector tubecollar 134 moves into the cavity 140 and proceeds toward the oil sealcover 142. While allowing hydraulic fluid to exit from the cavity 140,the dashpot orifices 150 also serve as a restriction on the rate atwhich the hydraulic fluid is able to exit the cavity, such that there isa natural back pressure applied against the connector tube collar 134counteracting the pressure that is being exerted by that collar as itproceeds in the direction of the arrow 143 (presumably due to acombustion event). The amount of back pressure applied against theconnector tube collar 134 is generally a function of piston speed (thehigher the piston velocity, the higher the pressure), and consequentlythe flow through the dashpot orifices 150 acts as a speed brake.

Often, the restriction upon hydraulic fluid flow provided by the dashpotorifices 150 is sufficient to completely stop movement of the connectortube collar 134 along the direction of the arrow 143 before the collarreaches the dashpot orifices. However, when the piston speed issufficiently high (e.g., when the force applied to the piston 62 withinthe cylinder 12 is particularly large), the connector tube collar 134can proceed far enough into the cavity 140 such that it begins to passby the dashpot orifices 150 or even completely passes by those orifices.As this occurs, for hydraulic fluid to exit the cavity 140, thehydraulic fluid first flows from the cavity between the outer diameterof the connector tube collar 134 and the inner diameter of the capacitorcase 138. The hydraulic fluid flowing within this narrow annular spacethen can exit either by way of the dashpot orifices 150 or by travelingentirely past the connector tube collar 134. Regardless of theparticular flow path(s) that occur, it should be evident that, as theconnector tube collar 134 moves partly or entirely over and past thedashpot orifices, significantly increased amounts of resistance tomovement toward the oil seal cover 142 are experienced by the connectortube collar. Because of this increased resistance, it is almost neverthe case that the connector tube collar 134 actually reaches the oilseal cover 142.

Although in the present embodiment hydraulic fluid exiting the capacitorcases 138 by way of the dashpot orifices 150 remains within thecylinders 10, 12, in other embodiments the fluid exiting the dashpotorifices can be directed to other locations. For example, in at leastsome embodiments, the engine employs the same hydraulic fluid as islocated within the cylinders and provided to the hydraulic wheel motorand auxiliary power unit hydraulic motor/flywheel also as coolant forthe engine. That is, in some such embodiments, the engine does notemploy any radiator or any separate fluid (such as ethylene glycol) tocool the engine, but rather utilizes as coolant the very same hydraulicfluid as is used to transmit power within the engine, and the movementof the pistons within the cylinders powers movement of the coolantthrough the cooling system. It will be understood that, in suchembodiments, the dashpot orifices 150 are the initial segments ofcooling channels extending within other portions of the engine body suchas the main engine housing 102, cylinder heads 112, and cylindricalsleeves 114 of FIG. 4. The hydraulic fluid that is diverted by way ofthe dashpot orifices to the cooling system, after passing through thecooling system, is typically returned to the main reservoir (e.g., thereservoir 70). Notwithstanding the above description, it will further beunderstood that the present invention is intended to encompass a varietyof engines having a variety of different types of cooling systemsemploying a variety of types of coolant, cooling devices (includingand/or not including radiators, fans, and the like), passages, and otherstructures.

As will be described further below with respect to FIGS. 8-13, in thepresent embodiment, the timing of various components of the engine 4 isdetermined by the electronic control circuitry 116 that, at least inpart, utilizes information regarding the positions of the pistons 62(and associated piston assemblies, such as the piston assembly 67) todetermine what actions to take or not take. In the present embodiment,to determine the positioning of the pistons 62, the electronic controlcircuitry 116 is provided with electrical signals from sensorsassociated with the dashpot assemblies 136 that are indicative of thepositioning of the connector tube collars 134 relative to those dashpotassemblies, and thus further indicative of the positioning of thepistons 62 within the same respective cylinders relative to the dashpotassemblies of those cylinders. The electrical signals in particular arereflective of changes in capacitance that occur as the connector tubecollars vary in their positions relative to their respective dashpotassemblies.

Further as shown in FIG. 5A, the dashpot assembly 136 includes anannular insulator 152 positioned between the second cylindrical portion148 of the capacitor case 138 and the oil seal cover 142. As shown, theannular insulator 152 has the same inner diameter of the cylindricalportions 146 and 148. The annular insulator 152 can be, for example, aflat ring fabricated from a relatively high dielectric material such asG11 epoxy board, and be approximately 0.06 inches thick. The annularinsulator 152 does not entirely separate the capacitor case 138 from theoil seal cover 142 insofar as fasteners (e.g., four screws) are used toattach the capacitor case to the oil seal cover, with the insulator inbetween. To ensure proper insulation, feed-thru bushings also made ofG11 epoxy are used in the area where the fasteners travel through theoil seal cover 142.

Due to the annular insulator 152, an ambient capacitance exists betweenthe capacitor case 138 and the oil seal cover 142, as well as betweenthe capacitor case and the components forming the wall of the cylinder12 (e.g., the main engine housing 102, cylinder head 112 of thatcylinder, and cylindrical sleeve 114 of that cylinder as shown in FIG.4). The connector tube 66 with its connector tube collar 134 can beconsidered to be in contact with an electrical ground formed by thesecomponents forming the wall of the cylinder 12, since the connector tube66 generally has some electrical contact with the walls of the cylinderdue to the piston rings that are in contact with the wall of thecylinder (again, the piston rings are typically metallic). At the sametime, due to the presence of non-conductive hydraulic fluid within thehydraulic chamber 64 of the cylinder 12 that separates the connectortube 66 and its connector tube collar 134 from the capacitor case 138,the capacitor case in particular is insulated from the connectortube/connector tube collar. Consequently, the capacitor case 138 andconnector tube collar 134 in particular are able to effectively form twoplates of a variable capacitor, where the capacitance varies withmovement of the collar relative to the capacitor case and in particularchanges significantly as the collar enters and travels within thecapacitor case (such process often taking less than 5 milliseconds). Thesensed capacitance changes, which are indicative of piston location, canbe sensed at an electrode locking clamp (or simply electrode) 154 on thecapacitor case 138, which in turn is connected to the electronic controlcircuitry 116 as shown in FIG. 12.

Turning to FIG. 5B, a partially cross-sectional, partially cut away (andpartially schematic) side elevation view is provided showing portions ofone of the cylinders 10 and 12 (namely, the cylinder 12), including oneof the cylinder heads 112 of such cylinder along with associatedcomponents that can be mounted upon or within that cylinder head. Also,FIG. 5B shows the piston 62 within the cylinder 12 to be at a top deadcenter position, and the combustion chamber 22 formed within thecylinder by the piston and walls of the cylinder. Although FIG. 5B inparticular is directed to the cylinder 12, it is equally representativeof the cylinder head components associated with the other cylinders 10,14, 16, 50 and 52 of the engine 4 of FIG. 2.

More particularly with respect to the components mounted upon/within thecylinder head 112, FIG. 5B shows the cylinder head 112 to include arespective one of the intake valves 26, a respective one of the exhaustvalves 28, a respective one of the fuel injectors 32, and a respectiveone of the sparking devices 24. The cylinder head 112, and particularlya portion of the cylinder head in which is formed a main inductioncavity 700, can be considered as the pressurized induction module 30 ofthe cylinder 12. Further as shown, in the present embodiment, each ofthe intake and exhaust valves 26 and 28 are poppet-type valves havingrespective valve heads 704 and respective valve stems 706. Each of therespective valve heads 704 is capable of resting against, and in thepresent view is shown to be resting against, a respective valve seat 708mounted within the cylinder head 112. Additionally, the main inductioncavity 700 extends between the respective valve seat 708 associated withthe intake valve 26 and an input port 710, by which the main inductioncavity receives pressurized air from the air tank 36 by way of one ofthe links 56 (see FIG. 2). By contrast, an exhaust cavity 702 extendsbetween the respective valve seat 708 associated with the exhaust valve28 and an output port 712, which can lead to the outside environment orto an exhaust processing system (e.g., a catalytic converter).

Also as shown, the intake valve 26 extends through the main inductioncavity 700 along an axis 714, and further extends beyond the maininduction cavity through the cylinder head 112 via a valveguide/passageway 718 up to an intake plunger chamber 720 (the valve stembeing slip-fit within the valve guide/passageway) formed within thecylinder head 112. Similarly, the exhaust valve 28 extends through theexhaust cavity 702 along an axis 716, and further extends beyond theexhaust cavity via a valve guide/passageway 722 up to an exhaust plungerchamber 724 (again with the valve stem being slip-fit within the valveguide/passageway) also formed within the cylinder head 112. A cover 726of the cylinder head 112 serves as an end portion of the cylinder headand also serves to form end walls of the plunger chambers 720 and 724.In at least some embodiments, the valve guide/passageway 722 has aslightly larger diameter than the valve guide/passageway 718, to allowfor greater heat expansion of the exhaust valve stem 706. Although therespective plunger chambers 720 and 724 are substantially sealed fromthe main induction cavity 700 and exhaust cavity 702, respectively,there can be some small amount of leakage between the respectivecavities and chambers by way of the respective valve guides/passageways718 and 722, respectively. Leakage of air in this manner can serve tocool the valves 26, 28, and generally does not undermine operation ofthe valves 26, 28.

Located within the respective plunger chambers 720 and 724,respectively, at respective far ends 728 of the intake and exhaustvalves 26 and 28, respectively (which are opposite the respective valveheads 704 of those valves), are respective plungers 730 and 732 of thosevalves. The plungers 730, 732 are generally cylindrical structureshaving diameters greater than the valve stems 706 of the valves 26, 28.At least certain portions of the respective plungers 730, 732 have outerdiameters that are substantially equal to (albeit typically slightlyless than) corresponding inner diameters of the respective plungerchambers 720 and 724, respectively. O-rings 734 are fitted intocircumferential grooves around the outer circumferences of the plungers730, 732. Consequently, respective inner portions 736 of the respectiveplunger chambers 720, 724 are substantially sealed relative torespective outer portions 738 of those plunger chambers by therespective plungers 730, 732 with their O-rings 734. In the presentembodiment, the plunger 730 of the intake valve 26 has a larger diameterthan the plunger 732 of the exhaust valve 28, although in alternateembodiments the diameters can be the same (or even the plunger 732 canhave the larger diameter).

In the view provided, the valves 26, 28 are both in closed positionssuch that the air/fuel mixture within the main induction cavity 700cannot be delivered to the combustion chamber 22 within the cylinder 12,and such that any exhaust byproducts within the combustion chambercannot be delivered from that chamber into the exhaust cavity 702.However, actuation of the respective valves 26, 28 causes those valvesto open, more particularly, by moving along their axes 714, 716 in adirection indicated by an arrow 740.

In contrast to many conventional engines that employ camshafts andvarious valve train components, in the present embodiment the openingand closing of the valves 26, 28 is accomplished electronically andpneumatically. More particularly, pressurized air supplied to the maininduction cavity 700 is further communicated to input ports 745 of botha first 4-way solenoid-actuated poppet valve 742 and a second 4-waysolenoid-actuated poppet valve 744 (electronic control signals beingprovided to these valves from the electronic control circuitry 116) byway of lines 746. First and second output ports 748 and 750,respectively, of the first poppet valve 742 are coupled by lines 756 tothe respective inner portion 736 and outer portion 738 of the intakeplunger chamber 720, while first and second output ports 752 and 754,respectively, of the second poppet valve 744 are coupled by others ofthe lines 756 to the respective inner portion 736 and outer portion 738of the exhaust plunger chamber 724. Based upon the position of the firstpoppet valve 742, the pressurized air is either supplied to the innerportion 736 or the outer portion 738 of the intake plunger chamber 720and, complementarily, the outer portion or the inner portion of thatplunger chamber is exhausted to the outside environment (by way of anexhaust port 755). Likewise, based upon the position of the secondpoppet valve 744, the pressurized air is either supplied to the innerportion 736 or the outer portion 738 of the exhaust plunger chamber 724and, complementarily, the outer portion or the inner portion of thatplunger chamber is exhausted to the environment.

FIG. 5B in particular shows both of the poppet valves 742, 744 to bepositioned such that pressurized air is directed to the inner portions736 of both of the plunger chambers 720, 724. Due to the interaction ofthis pressurized air with the plungers 730, 732, both the intake valve26 and the exhaust valve 28 are in their closed positions as shown.Particularly with respect to the intake valve 26, the pressure exertedby the pressurized air within the main intake conduit 700 upon the valvehead 704 tending to open the valve is outweighed by the pressure exertedby the pressurized air within the inner portion 736 of the intakeplunger chamber 720, since in the present embodiment the plunger 730 hasa surface area greater than the exposed portion of the valve head. Also,when the valves are closed, the pressures experienced at opposite endsof the valve guides/passageways (e.g., the pressures within the cavity700 and the inner portions 736 of the plunger chambers 720, 724) areidentical.

Upon actuating the first poppet valve 742 so as to direct thepressurized air to the outer portion 738 of the intake plunger chamber720, however, the intake valve 26 is moved in the direction of the arrow740 and forced open. Similarly, upon actuating the second poppet valve744 so as to direct the pressurized air to the outer chamber 738 of theexhaust plunger chamber 724, the exhaust valve 28 is moved in thedirection of the arrow 740 and force open. Actuation of the poppetvalves 742, 744 causes the valves 26, 28 to open fast enough (e.g.,within 10 ms or less), and leakage through the valve guides/passageways718, 722 is typically slow enough, that no appreciable changes in thepressures within the inner portions 736 of the plunger chambers 720, 724due to such leakage occurs through those guides/passageways. Therelatively large diameter of the plunger 730 is advantageous insofar asit helps guarantee that the intake valve 26 will open. Further, althoughnot necessarily the case, in the present embodiment the volume occupiedby the plunger 732 within the exhaust plunger chamber 724 is relativelylarge (and larger than the volume occupied by the plunger 730 within thechamber 720) so that relatively little time is required to fill in theouter portion 738 of the chamber 724 with pressurized air, thus leadingto a quicker response in the opening of the exhaust valve 28.

Particularly with respect to the intake valve 26, the speed with whichthe intake valve opens is further enhanced by the influence of thepressurized air within the main induction cavity 700 upon the valve head704 of the intake valve 26. The speed of air (and fuel) entry issufficiently great that the process can be termed “pressure waveinduction”, and the complete induction process can in some embodimentstake less than 10 ms (or even a shorter time when operating the engineat less than full throttle). In at least some embodiments, the fuelinjector 32 is energized slightly before the intake valve 26 opens, sothat virtually all of the fuel injected for a given combustion stroke ofthe engine will be swept into the combustion chamber and used duringthat stroke. The time during which the second poppet valve 744 isactuated, which controls the opening of the exhaust valve 28, isgenerally longer than the time during which the first poppet valve 742is actuated, and the timing of the former can be of particularsignificance in terms of causing appropriately-timed closing of theexhaust valve.

In general, because the induction of fuel/air into the combustionchamber 22 is accomplished electronically and pneumatically, any mannerof timed actuation of the valves 26, 28 can be performed. Further, incomparison with some valves that are moved strictly electronically byway of solenoid actuation, the presently-described manner of actuatingvalves is advantageous in certain regards. In particular, because thevalves 26, 28 in the present embodiment are piloted (controlled)electronically by the poppet valves 742, 744 but driven pneumatically asa result of the compressed air, actuation of the valves 26, 28 can beachieved in a manner that is not only rapid and easily controlled, butalso requires only relatively low voltages/currents to drive thesolenoids of the poppet valves. Additionally it should be further notedthat, while actuation of the valves 26, 28 over times on the order of 10ms is not particularly fast in terms of valve actuation, it issufficient for the present embodiment of the engine 4. As will bedescribed further below, the present embodiment of the engine is able toprovide greater torque that many conventional engines. Because theengine has more torque, it can run slower than a comparablecrankshaft-based engine. Further, although the embodiment of FIG. 5Bshows the pressurized air to be applied to the surfaces of the plungers730, 732 in order to actuate the valves 26, 28, in other embodimentspressurized air can alternatively be applied other components (e.g.,components coupled to the valves) that in turn cause actuation of thevalves.

Turning to FIGS. 6A-6D, during normal operation of the engine 4, thepiston assemblies within the engine 4 such as the piston assembly 67such as that described with respect to FIGS. 4 and 5A (as well as thepiston assemblies within the other pairs of cylinders 14, 16 and 50, 52)move back and forth between respective first and second end-of-travel(EOT) positions. FIGS. 6A-6D respectively provide four exemplary viewsof the cylinder assembly 100 as its piston assembly 67 arrives at, andmoves between, such first and second EOT positions. More particularly,FIGS. 6A and 6C respectively show the piston assembly 67 to be at thefirst and second EOT positions, which in the present example are leftand right EOT positions (albeit in any given arrangement those positionsneed not be described as being leftward or rightward relative to oneanother), while FIGS. 6B and 6D show the piston assembly 67 to be atintermediate positions moving from the left EOT position to the rightEOT position and vice-versa, respectively.

Referring to FIG. 6A in particular, the piston assembly 67 as shown isat the left EOT position (similar to the position shown in FIG. 4),where the combustion chamber 22 associated with the first cylinder 10 isreduced in size and the combustion chamber of the second cylinder 12 islarger in size. By referring to this position of the piston assembly 67as the left EOT position, this is not to say that the piston assembly 67necessarily has moved to its maximum position towards the left (e.g., inthe direction indicated by the arrow 143), such that the connector tubecollar 134 within the second cylinder 12 reaches the oil seal cover 142within the dashpot assembly 136 of that cylinder (as shown in FIG. 5A),much less that the piston 62 within the first cylinder 10 reaches thecylinder head 112 of that cylinder. Rather, in the present embodiment(albeit not necessarily in all embodiments), the left EOT positionshould be understood as encompassing a positional range in which theconnector tube collar 134 within the cylinder 12 has proceeded farenough into the dashpot assembly 136 associated with that cylinder suchthat a threshold capacitance change has occurred as determined by theelectronic control circuitry 116 based upon the signals received fromthat dashpot assembly via the electrode 154. For purposes of discussionbelow, each of the electrodes 154 associated with the two dashpotassemblies 136 of the cylinder assembly 100 can be considered acapacitance sensor and, more particularly, an EOT sensor.

In contrast to FIG. 6A, FIG. 6C shows the piston assembly 67 of thecylinder assembly 100 to have shifted to the opposite, right EOTposition such that the combustion chamber 22 associated with the secondcylinder 12 is reduced in size and the combustion chamber associatedwith the first cylinder 10 is expanded in size. Again, the attainment ofthe right EOT position does not necessarily require that the connectortube collar 134 associated with the first cylinder 10 necessarily bepositioned so far into the dashpot assembly 136 of that cylinder suchthat the connector tube collar impacts the oil seal cover 142 of thatdashpot assembly, or that the piston 62 within the second cylinder 12impact the cylinder head 112 of that cylinder. Rather, in the presentembodiment, the attainment of the right EOT position entails thepositioning of the connector tube collar 134 of the first cylinder 10far enough into the dashpot assembly 136 of that cylinder such that athreshold capacitance change as determined by the electronic controlcircuitry 116 has occurred. As for FIG. 6B, that figure shows the pistonassembly 67 to be moving along a direction indicated by an arrow 145 tothe right (opposite to the direction of the arrow 143), away from theleft EOT position of FIG. 6A toward the right EOT position of FIG. 6C.In contrast, FIG. 6D shows the piston assembly 67 in progress as it ismoving back from the right EOT position of FIG. 6C back toward the leftEOT position of FIG. 6A, along the direction of the arrow 143.

In addition to showing various positions of the piston assembly 67,FIGS. 6A-6D also show in schematic form the various input and outputdevices employed in conjunction with the cylinder assembly 100 that canbe controlled and/or monitored by the electronic control circuitry 116.More particularly, each of FIGS. 6A-6D show the sparking devices 24, theintake valves 26, the exhaust valves 28, and the fuel injectors 32associated with each of the cylinders 10, 12 (particularly the cylinderheads) of the cylinder assembly 100. The respective fuel injectors 32 inparticular are shown to be linked to the respective intake valves 26 byway of the respective pressurized induction modules 30 that, althoughnot controlled devices themselves, nonetheless are configured to receivethe fuel from the fuel injectors 30 as well as pressurized air from thelinks 56 (see FIG. 2) and to provide that fuel/air mixture to therespective intake valves 26. Further as shown in FIGS. 6A-6D, each ofthe cylinder assemblies 100 is shown to include the electrodes/EOTsensors 154 associated with the first and second cylinders 10 and 12,respectively. The EOT sensors 154 shown are intended to signify thatoutput signals indicative of capacitance and particularly indicative ofcapacitance levels associated with movement of the piston assembly 67 toits right and left EOT positions can be provided from those sensors.

Given that a pair of each of the components 24-32 and 154 is shown to beimplemented with respect to the cylinder assembly 100, and given that afirst of each of those pairs of components is associated with the firstcylinder 10 toward which the piston assembly 67 moves to attain the leftEOT position while a second of each of those pairs of components isassociated with the second cylinder 12 toward which the piston assemblymoves to attain the right EOT position, henceforth for simplicity ofdescription those first components associated with the first cylinderwill be referred to as the respective “left” components of the cylinderassembly while those second components associated with the secondcylinder will be referred to as the respective “right” components of thecylinder assembly. It should be noted that, given this convention, the“right” EOT sensor within the second cylinder 12 senses whether thepiston assembly 67 has reached the left EOT position, while the “left”EOT sensor within the first cylinder 10 senses whether the pistonassembly has reached the right EOT position.

Notwithstanding this convention employed in the present description, itshould at the same time be understood that this convention is merelybeing employed for convenience herein, and that any given embodiment ofthe present invention need not in particular have pairs of componentsthat are oriented in a leftward or rightward manner with respect to anyarbitrary reference point. Indeed, regardless of any particulardescriptive language used herein, the present invention is intended toencompass a wide variety of embodiments having components arrangedrelative to one another and to other reference points in a variety ofmanners, and not merely the particular arrangements shown herein.

Turning to FIG. 7, a flow chart 157 shows exemplary steps ofoperation/actuation of the components 24-32 and 154 associated with thecylinder assembly 100 that are performed in order to move the pistonassembly 67 therein between the left and right EOT positions asillustrated by the FIGS. 6A-6D. As shown, when the piston assembly 67arrives at the left EOT position as represented by FIG. 6A, the arrivalof the piston assembly at this position is sensed at a step 160 by wayof the right EOT sensor 154 at the right dashpot assembly 136 when thatdashpot assembly receives the right connector tube coupler 134 andconsequently a threshold capacitance change occurs. Next, at a step 162,the left exhaust valve 28 is closed and further, at a step 164, theright exhaust valve 28 is opened. The exact timing of the closing of theleft exhaust valve 28 relative to the arrival of the piston assembly 67at the left EOT position in at least some embodiments depends on enginespeed as determined via an engine speed sensor (as further describedbelow with respect to FIG. 13).

Subsequently, at a step 166, the left fuel injector 32 is switched on tobegin a pulsing of fuel into the left pressurized induction module 30.Then, at a step 168, the left intake valve 26 is opened and, at a step170, the fuel/air mixture received by the left pressurized inductionmodule 30 from the left fuel injector 32 and from the air tank 36 (byone of the links 56) is inducted into the left combustion chamber 22 atvery high speeds. The timing difference between the time at which thefuel injector 32 begins spraying and the time at which the intake valvephysically opens can be approximately 5 to 10 ms, and this delay isadvantageous for allowing fuel to enter completely into the combustionchamber; nevertheless, in other embodiments this delay may be negligibleor zero. Eventually, at a step 172, the left fuel injector 32 isswitched off to stop pulsing fuel into the left pressurized inductionmodule 30 and, at a step 174, the left intake valve 26 is closed. Oncethis has occurred, the appropriate amount of fuel/air mixture has beenprovided into the left combustion chamber 22. At this time the leftsparking device 24 is fired at a step 176, as a result of whichcombustion is initiated as represented by a step 178. Once thecombustion is initiated, the piston assembly 67 begins to move rightwardin the direction of the arrow 145 as shown in FIG. 6B. During this timeperiod, the right exhaust valve 28 remains open while all of the othervalves (e.g., the left intake and exhaust valves as well as the rightintake valve) remain closed, as indicated by a step 182.

As corresponds to FIG. 6C, the piston assembly 67 in the present examplecontinues to move rightward until it arrives at the right EOT position.The arrival of the piston assembly 67 at this position is sensed by wayof the left EOT sensor 154 associated with the left dashpot assembly 136when that dashpot assembly receives the left connector tube collar 134and consequently a threshold capacitance change occurs at that dashpotassembly, at a step 184. After the arrival at the right EOT position hasbeen sensed, at steps 186 and 188 the right and left exhaust valves 28are closed and opened, respectively. As with the left exhaust valve 28,the exact timing of the closing of the right exhaust valve relative tothe arrival of the piston assembly 67 at the right EOT position in atleast some embodiments depends on engine speed as determined via anengine speed sensor (as further described below with respect to FIG.13). In any event, subsequent to the steps 186 and 188, at a step 190the right fuel injector 32 is turned on, causing it to begin pulsingfuel into the right pressurized induction module 30. Next, at a step192, the right intake valve 26 is opened such that, at a further step194, the fuel/air mixture is inducted from the right pressurizedinduction module 30 into the right combustion chamber 22.

Eventually, at a step 196, the right fuel injector 32 is switched offand then, at a step 198, the right intake valve 26 is closed. Once thishas occurred, the appropriate amount of fuel/air mixture has beenprovided into the right combustion chamber 22. Then, at a step 199, theright sparking device 24 is fired, thus causing combustion to beginwithin the right combustion chamber 22 at a step 156. Upon theinitiation of combustion, the piston assembly 67 moves leftward asrepresented by the arrow 143 of FIG. 6D. During this time, the leftexhaust valve 28 remains open as represented by a step 158, allowingexhaust products resulting from the previous combustion event of thestep 178 to exit the left combustion chamber 22. Additionally duringthis time, all of the other valves (e.g., the right intake and exhaustvalves as well as the left intake valve) remain closed, as representedby a step 159. After this time, the sequence of the flow chart 157 canreturn to the step 160 as the piston assembly 67 again reaches the leftEOT position, as represented by a return step 155.

Referring additionally to FIG. 8, a timing diagram 200 furtherillustrates exemplary timing of the actuation of the various components24-32, 154 (and certain related timing characteristics) when thosecomponents are operated in the manner shown in FIGS. 6A-7 in which thepiston assembly 67 is driven back and forth between the left and rightEOT positions. The timing diagram 200 in particular shows twelvedifferent graphs 202-224 that represent the various statuses of thecomponents 24-32, 154 (as well as certain differences between thosesignals that are of interest). As shown, at a first time T₁ at which thepiston assembly 67 arrives at the left EOT position, a left EOT positiongraph 202 is shown to switch from a low value to a high value indicatingthat the capacitance as sensed by the right EOT sensor 154 has reached athreshold. In the present embodiment when this occurs, a left exhaustvalve graph 204 immediately switches off (e.g., switches from a highvalue to a low value), corresponding to a command that the left exhaustvalve 28 be closed, and also a right exhaust valve graph 206 transitionson (e.g., switches from a low value to a high value), corresponding to acommand that the right exhaust valve be opened.

Subsequent to the time T₁, at a time T₂, a left fuel injector graph 210switches on, corresponding to the initiating of the pulsing of fuel intothe left pressurized induction module 30 by the left fuel injector 32.Also at the time T₂, a left intake valve graph 212 switches on,indicating that the left intake valve 26 has been opened (or at least isbeginning to open) such that the fuel/air mixture within the leftpressurized induction module 30 can enter into the left combustionchamber 22. The difference between the times T₂ and T₁ is furtherillustrated by a left intake valve delay graph 208, and that differencein the times in particular is set so as to provide sufficient time toallow the left exhaust valve 28 to close (it does not do soinstantaneously) prior to the opening of the left intake valve 26.Subsequently, at a time T₃, the left fuel injector graph 210 againswitches off, corresponding to the cessation of pulsing of the left fuelinjector 32. Then, at a time T₄, the left intake valve graph 212 alsoswitches low, indicating that the left intake valve 26 has been closedsuch that no further amounts of fuel/air mixture can proceed into theleft combustion chamber 22. Next, at a time T₅, a left sparking devicegraph 214 transitions from a low level to a high level, indicating thatthe left sparking device 24 has been actuated. A sparking delay graph216 illustrates the amount of delay time that occurs between the timesT₄ and T₅.

After transitioning high at the time T₅, the left sparking device graph214 remains at a high level until a time T₆, at which time it returns toa low level, signifying that the left sparking device 24 has beenswitched off again. Although actuation of the left sparking device 24within the time period between the times T₅ and T₆ can involve a singletriggering of that device to produce only a single spark (e.g., at orslightly after the time T₅), in alternate embodiments the actuation ofthe left sparking device can involve repeated (e.g., periodic)triggering of that device to produce multiple sparks within that timeperiod. This can be appropriate in at least some circumstances where thecombustion event resulting from a single spark within the leftcombustion chamber 22 might leave a portion of the fuel/air mixturewithin the chamber uncombusted, but repeated sparks over a period oftime better guarantees that all (or substantially all) of the fuel/airmixture within the left combustion chamber 22 has been combusted.

Regardless of the particular manner in which the left sparking device 24is actuated, due to the sparking activity, combustion occurs within theleft combustion chamber 22 and, as a result, the piston assembly 67 ismoving to the right along the direction of the arrow 145 as shown inFIG. 6B. Consequently, at a time T₇, the piston assembly 67 has movedsufficiently far to the right that it is no longer in the left EOTposition, and consequently the left EOT position graph 202 switches off.Subsequent to the time T₇, all of the graphs 202-216 remain at lowlevels until a time T₁₁, with the exception of the graph 206representing actuation of the right exhaust valve 28, which remains highsince the right exhaust valve 28 remains open. During this time periodbetween the times T₇ and T₁₁, the piston assembly 67 continues to movein the direction 145.

At the time T₁₁, the left dashpot assembly 136 receives the leftconnector tube collar 134 to a sufficient degree that the left EOTsensor 154 produces a signal indicative of a capacitance that hasincreased above a threshold level. Thus, at this time, a right EOTposition graph 218 transitions from a low level to a high level. Uponthis occurring, also at the time T₁₁, the left exhaust valve graph 204immediately is transitioned from a low level to a high level and theright exhaust valve graph 206 is transitioned from a high level to a lowlevel, such that the left exhaust valve 28 is caused to open and theright exhaust valve is caused to close. Subsequently, at a time T₁₂(which occurs after the time T₁₁ by an amount of time sufficient toallow the right exhaust valve to close, as shown by the intake valvedelay graph 208), a right fuel injector graph 220 switches from a lowlevel to a high level, indicating that the right fuel injector 32 beginsthe pulsing of fuel into the right pressurized induction module 30. Alsoat this time, a right intake valve graph 222 transitions from a lowlevel to a high level, such that the fuel/air mixture within the rightpressurized induction module 30 can enter the right combustion chamber22 of the cylinder assembly 100.

Similar to the discussion regarding the left fuel injector and leftintake valve graphs 210 and 212, respectively, the right fuel injectorgraph 220 is subsequently switched off at a time T₁₃ and the rightintake valve graph 222 is switched off at a time T₁₄. Subsequently, at atime T₁₅, which occurs subsequent to the time T₁₄ by an amount indicatedby the sparking delay graph 216, a right sparking device graph 224 isswitched high and then switched low again at a time T₁₆, and thus theright sparking device 24 is switched on between those times. Due to theactuation of the right sparking device 24 (which again, as describedabove, can involve the production of only a single spark or,alternatively, multiple sparks), combustion occurs within the rightcombustion chamber 22. This in turn causes movement of the pistonassembly 67 along the direction indicated by the arrow 143 as shown inFIG. 6D. This movement of the piston assembly 67 eventually moves thepiston assembly sufficiently far that the right EOT position graph 218switches from a high value to a low value at a time T₁₇. Furthermovement of the piston assembly 67 in this direction eventually returnsthe piston assembly back to the left EOT position at a time T₂₁.Beginning at that time T₂₁, the operations described as occurring attimes T₁-T₇ again occur, respectively. That is, at times T₂₁-T₂₇, theoperations that occurred at the times T₁-T₇ are repeated. Thus, thecycle of operation can repeat indefinitely.

While FIGS. 6A-8 envision that movement of the piston assembly 67 withinthe cylinder assembly 100 always will proceed in a manner such that thepiston assembly moves back and forth between the right and left EOTpositions in response to combustion events occurring in the combustionchambers 22 of the cylinder assembly, and while this is true normally,in some circumstances operation does not and/or cannot proceed in thismanner. In particular, in some circumstances (e.g., when the load uponthe hydraulic wheel motor 18 is great), a given combustion event willnot impart sufficient force upon the piston assembly 67 so as to causethe piston assembly to proceed all of the way to the EOT position withinthe cylinder opposite the cylinder at which the combustion eventoccurred. For example, if a combustion event occurs within the leftcombustion chamber 22 within the first cylinder 10 and the load upon thehydraulic chamber 64 within that same cylinder is particularly great atthat time, the piston assembly 67 in that circumstance may notsuccessfully move all of the way to the right EOT position in responseto that combustion event but otherwise may stop moving somewhere inadvance of the right EOT position.

Indeed, in some circumstances, it is also possible that neither the leftnor the right EOT positions will be attained by the piston assembly 67even though the piston assembly continues to be moved back and forthwithin the cylinder assembly 100 as a result of combustion events.Alternatively, in still other circumstances, it is possible that theforce imparted to the piston assembly 67 during a given combustion eventwill be too low even to move that piston assembly 67 out of the EOTposition in which it currently resides. In each of these circumstances,the manner of movement experienced by the piston assembly 67 within thecylinder assembly 100 will differ from that shown in FIGS. 6A-6D,particularly insofar as, depending upon the type of movement, the pistonassembly 67 will not experience one or both of the EOT positions shownin FIGS. 6A and 6C, or will only experience one of the EOT positions ofFIGS. 6A and 6C but not experience any of the other three positionsshown in FIGS. 6A-6D. Further, in such operational circumstances, thesequence of events/timing will differ from that shown in FIGS. 7-8.

Referring to FIGS. 9-11, additional timing diagrams 300, 400 and 500,respectively, illustrate exemplary timing of the actuation of thevarious components 24-32, 154 (and certain related timingcharacteristics) when those components are operated in the threeabove-described “abnormal” modes of operation in which the pistonassembly 67 fails to attain one or both of the EOT positions or remainswithin one of the EOT positions despite combustion events that shoulddrive the piston assembly from that EOT position. Although the differentmanners of operation shown by FIGS. 9-11 are shown separately from oneanother and from the normal mode of operation of FIG. 8, it will beunderstood that the electronic control circuitry 116 is capable ofcontrolling the engine 4 so that it operates to enter, exit from andswitch between any of these modes of operation repeatedly andseamlessly, with no noticeable effect on operation.

Referring particularly to FIG. 9, the timing diagram 300 in particularillustrates exemplary timing of the actuation of the various components24-32, 154 (and certain related timing characteristics) of the cylinderassembly 100 when the piston assembly 67 is able to attain and leave theleft EOT position but is not able to attain the right EOT position.Although the timing diagram 300 shows exemplary operation in which thepiston assembly 67 is capable of attaining and exiting the left EOTposition but fails to attain the right EOT position, it will beunderstood that the manner of operation corresponding to the oppositemanner of piston movement (e.g., where the piston assembly is capable ofattaining and exiting the right EOT position but fails to attain theleft EOT position) would be substantially the opposite of that describedbelow.

More particularly, in the present example, when the piston assembly 67attains the left EOT position at a time T₁, the operation initiallyproceeds in much the same manner as was the case in FIG. 8. That is, atthe time T₁, a left EOT position graph 302 transitions from low to highwhen the cylinder assembly 67 has attained the left EOT position andconsequently, at that time, a left exhaust valve graph 304 switches lowso as to close the left exhaust valve 28 and a right exhaust valve graph306 switches high so as to open the right exhaust valve 28. Then, at atime T₂ (which differs from the time T₁ by an amount of time shown by anintake valve delay graph 308), a left fuel injector graph 310 switcheshigh, as does a left intake valve graph 312, thus turning on the fuelinjector 32 and opening the left intake valve 26. Then, at a time T₃,the left fuel injector graph 310 switches low and at a time T₄ the leftintake valve graph 312 switches low, so as to turn off the left fuelinjector 32 and close the left intake valve 26, respectively. Further,at the times T₅ and T₆, a left sparking device graph 314 switches highand low, respectively, such that the left sparking device 24 is turnedon and then off at those respective times (where the time T₅ occurssubsequent to the time T₄ by an amount of time indicated by a sparkingdelay graph 316). Finally, at the time T₇, the left EOT position graph302 switches back to a low value as the combustion event resulting fromthe left sparking device 24 causes the piston assembly 67 to leave theleft EOT position.

In contrast to the operation shown in FIG. 8, however, the timingdiagram 300 does not show at a time T₁₁ the switching of a right EOTposition graph 318 to a high level, since the piston assembly 67 in thisexample never attains that right EOT position. Rather, in this example,at a time T₃₁ the electronic control circuitry 116 determines that aperiod of time (in this example, equaling the difference between thetimes T₃₁ and T₅) has occurred since the beginning of the sparkingperformed by the left sparking device 24 and consequent commencement ofa combustion event within the left combustion chamber 22. As a result,at this time T₃₁, the electronic control circuitry 116 causes the engine4 to operate as if the right EOT position had been attained, even thoughit has not. Thus, at this time T₃₁, a right exhaust valve graph 306switches to a low level such that the right exhaust valve 28 is closed,and additionally the left exhaust valve graph 304 switches to a highlevel such that the left exhaust valve is opened.

Subsequently, at a time T₃₂ (which differs from the time T₃₁ by anamount of time shown by the intake valve delay graph 308), a right fuelinjector graph 320 switches from low to high and a right intake valvegraph 322 likewise switches from low to high, thus, causing fuel to beinjected into the right pressurized induction module 30 by the rightfuel injector 32 and causing fuel/air mixture to be provided into theright combustion chamber 22 via the right intake valve 26. Next, attimes T₃₃ and T₃₄, respectively, the right fuel injector graph 322 isswitched to a low value and likewise the right intake valve graph 322 isswitched to a low value, thus shutting off the right fuel injector 32and then closing the right intake valve 26, respectively. Further, at atime T₃₅ (which occurs subsequent to the time T₃₄ by an amount of timeindicated by the sparking delay graph 316), a right sparking devicegraph 324 switches from low to high, resulting in actuation of the rightsparking device 24. This continues until a time T₃₆, at which the rightsparking device graph 324 is again switched low. As a result of theactuation of the right sparking device 24, a combustion event within theright combustion chamber 22 occurs, and consequently the piston assembly67 again returns to the left EOT position at a time T₄₁, at which timethe left EOT position graph 302 again rises, the left exhaust valvegraph 304 again falls and the right exhaust valve graph 306 again rises.Subsequent to the time T₄₁, the graphs 302-324 all operate in the samemanner at respective times T₄₁-T₄₇ as occurred at the times T₁-T₇,respectively.

Referring next to FIG. 10, the timing diagram 400 illustrates exemplarytiming of the actuation of the various components 24-32, 154 (andcertain related timing characteristics) of the cylinder assembly 100when the piston assembly 67 is operating in another abnormal mode inwhich, though the piston assembly may be experiencing movement, thepiston assembly nevertheless fails to reach either the left EOT positionor the right EOT position. As shown, when the piston assembly 67 is inthis mode of operation, left and right EOT position graphs 402 and 418,respectively, both remain constant (e.g., at a low value) at all times,indicating that neither the left nor the right EOT positions arereached. Since the EOT positions are not reached, instead of basing theactuation of other components such as the valves 26 and 28, fuelinjectors 32 and sparking devices 24 based upon the times at which theEOT positions are reached (as determined via signals from the EOTsensors 154), instead those components are actuated at other timesdetermined by the electronic control circuitry 116.

More particularly, as shown in FIG. 10, the components 24, 26, 28 and 32are actuated at times referenced to successive times determined by theelectronic control circuitry 116 at which a timer has expired (timedout). Three such timed out conditions are shown in FIG. 10 to haveoccurred, namely, at times T₅₁, T₆₁ and T₇₁, albeit it will beunderstood that additional timed out conditions could occur indefinitelythereafter. In the example shown, the time T₅₁ begins a half cycle inwhich combustion occurs in the left combustion chamber 22 of the firstcylinder 10. More particularly, at the time T₅₁, a left exhaust valvegraph 404 is switched off and also a right exhaust valve graph 406 isswitched on, corresponding to the closing and opening of the left andright exhaust valves 28, respectively. Subsequently, at a time T₅₂(which differs from the time T₅₁ by an amount of time shown by an intakevalve delay graph 408), each of respective left fuel injector and leftintake valve graphs 410 and 412 are activated, resulting in opening ofthe left intake valve 26 and pulsing of the left fuel injector 32.

Subsequently, at a time T₅₃ the left fuel injector graph 410 transitionslow, indicating the switching off of the left fuel injector 32, and at atime T₅₄ the left intake valve graph 412 also transitions low,indicating closure of the left intake valve 26. Finally, at a time T₅₅,a left sparking device graph 414 transitions high (with the time T₅₅occurring subsequent to the time T₅₄ by an amount of time shown by asparking delay graph 416), turning on the left sparking device 24, andthen the left sparking device graph 414 transitions low at a time T₅₆,switching off the left sparking device. Thus, from this example, it isapparent that (at least in this embodiment) the actuation of the valves26 and 28, fuel injector 32 and sparking device 24 subsequent to thetime T₅₁ is identical to the manner in which those components areactuated subsequent to the time T₁ of FIGS. 8 and 9 when the pistonassembly 67 is starting at the left EOT position. However, in thepresent case, the basis for actuating these components in this manner isnot the arrival of the piston assembly 67 at the left EOT position, butrather is the arbitrary determination of the time T₅₁ by the electroniccontrol circuitry 116.

Further as shown, because in the present embodiment the combustion eventthat results from the actuation of the left sparking device 24 betweenthe times T₅₅ and T₅₆ does not result in movement of the piston assembly67 all of the way to the right EOT position (and can in somecircumstances not produce any movement at all), the time T₆₁ also is notdetermined based upon the arrival of the piston assembly at suchposition but rather is determined by the electronic control circuitry116 as the expiration of a timer relative to the time T₅₅ (or, inalternate embodiments, some other time such as the time T₅₆).Nevertheless, once this time T₆₁ has been determined, the components 24,26, 28 and 32 of the cylinder assembly 100 are actuated in substantiallythe same manner as was described above where the piston assembly 67reached the right EOT position. That is, at the time T₆₁, the leftexhaust valve graph 404 switches from a low level to a high level andthe right exhaust valve graph 406 switches from a high level to a lowlevel, thus opening the left exhaust valve 28 and closing the rightexhaust valve.

Subsequently, at a time T₆₂, (which occurs subsequent to the time T₆₁ byan amount of time shown by the intake delay graph 408), a right fuelinjector graph 420 is switched from low to high and also a right intakevalve graph 422 is switched from low to high, thus causing the rightfuel injector 32 to inject fuel into the right pressurized inductionmodule 30 and causing the right intake valve 26 to be opened,respectively. Subsequently, at a time T₆₅, the right fuel injector graph420 switches off, thus stopping the pulsing of the right fuel injector32, and then later at a time T₆₄, the right intake valve graph 422 isshut off, thus closing the right intake valve 26. Finally, at times T₆₅and T₆₆ (where the time T₆₅ follows by the time T₆₄ by an amount of timeindicated by the sparking delay graph 416), the right sparking devicegraph 424 switches on and then subsequently switches off, correspondingto the switching on and off of the right sparking device 24. Thisactuation of the right sparking device 24 again produces a combustionevent that tends to cause movement of the piston assembly 67 in theleftward direction (albeit, in some circumstances, little or no movementmay actually occur, for example if the vehicle is situated up against animmovable object).

Insofar as FIG. 10 is intended to show continued movements of the pistonassembly 67 back and forth between the first and second cylinders 10,12, where the piston assembly never reaches an EOT position, beginningat a time T₇₁ the components 24, 26, 28 and 32 are again actuated insuch a way as to cause a combustion event within the left combustionchamber 22 and cause movement of the piston assembly in the direction ofthe right combustion chamber. The time T₇₁ in particular again isdetermined by the electronic control circuitry 116 as a timing out of atimer relative to the time T₆₅ (or some other time). At and subsequentto the time T₇₁, the components 24, 26, 28 and 32 are actuated in thesame manner as was described earlier with respect to the time T₅₁ andsubsequent times thereafter. That is, the left exhaust valve and rightexhaust valve graphs 404 and 406 again switch their respective statusesat the time T₇₁, the left exhaust valve and left fuel injector graphs410 and 412 both are switched on at a time T₇₂ and then switched off attimes T₇₃ and T₇₄, respectively, and further the left sparking devicegraph 414 switches on and then off at times T₇₅ and T₇₆. In the eventthat the piston assembly 67 never reaches an EOT position at either ofthe cylinders 10, 12, the operation shown in FIG. 10 can continue onindefinitely.

As for FIG. 11, the additional timing diagram 500 provides additionalgraphs 502-524 that illustrate exemplary timing of the actuation of thevarious components 24-32, 154 (and certain related timingcharacteristics) of the cylinder assembly 100 when the piston assembly67 is operating in yet another abnormal mode. In this mode of operation,the piston assembly 67 remains at the left EOT position and, despitecombustion events occurring within the left combustion chamber 22, isunable to leave that left EOT position. Although the timing diagram 500shows exemplary operation in which the piston assembly 67 is unable toexit the left EOT position, it will be understood that the manner ofoperation corresponding to the opposite manner of operation (e.g., wherethe piston assembly is unable to exit the right EOT position) would besubstantially the opposite of that described below.

As shown in FIG. 11, the graphs 502-524 respectively are a left EOTposition graph 502, a left exhaust valve graph 504, a right exhaustvalve graph 506, an intake valve delay graph 508, a left fuel injectorgraph 510, a left intake valve graph 512, a left sparking device graph514, a sparking delay graph 516, a right EOT position graph 518, a rightfuel injector graph 520, a right intake valve graph 522, and a rightsparking device graph 524. In the present example, the piston assembly67 first arrives at the left EOT position at the time T₁ (as was assumedin FIGS. 8 and 9) and then remains at that left EOT position, asindicated by a left EOT graph 502. Correspondingly, a right EOT graph518 shows the piston assembly 67 to not be at the right EOT positionduring any of the time encompassed by the timing diagram 500 (albeit thepiston assembly could have been at such position prior to the time T₁).Upon commencing operation at the time T₁, the components 24, 26, 28 and32 are actuated in the same manner at that time and subsequent timesT₂-T₆ as was described earlier with respect to FIGS. 8 and 9.

Because the piston assembly 67 never leaves the left EOT position as aresult of the combustion event that occurs beginning at the time T₅, noswitching of the left EOT position graph 502 occurs at any time T₇, butrather at a time T₈₁ the electronic control circuitry 116 determinesthat a time has expired and causes further actuation of the componentsof 24, 26, 28 and 32 of the cylinder assembly 100. In particular,beginning at the time T₈₁, the actions taken at the times T₁-T₆described above are reperformed at times T₈₁-T₈₆, respectively (asidefrom the switching of the open/closed status of the exhaust valves 28,which stay in their current positions as indicated by the graphs 504 and506). Then, since in the present example the piston assembly 67continues to remain at the left EOT position, at a time T₉₁ theelectronic control circuitry again recognizes that the piston assemblyhas not moved out of the left EOT position and as a result repeats, attimes T₉₁-T₉₆, the operations already performed at the times T₈₁-T₈₆,respectively.

Turning to FIG. 12, exemplary communication links within the engine 4,particularly communication links between the electronic controlcircuitry 116 and various other components of the engine 4, are shown inmore detail. Typically, links such as those shown in FIG. 12 areaccomplished by way of electrical circuits, albeit other embodimentsemploying other manners of achieving such communication links are alsointended to be encompassed within the present invention. In particularas shown, the electronic control circuitry 116 is coupled to anaccelerator pedal 670 by which the electronic control circuitry detectsan operator-commanded acceleration (or velocity) setting, as well as anignition switch 672, by which the electronic control circuitry is ableto determine whether an operator has commanded the engine 4 to be turnedon or off (typically based upon the presence of a key within an ignitionswitch, albeit such command could also be provided by an operator'sentry of an appropriate code or another mechanism).

Further, the electronic control circuitry 116 is coupled to thehydraulic wheel motor 18 (more particularly, to a sensor at that wheelmotor), by which the electronic control circuitry is able to determinewheel (and thus vehicle) speed. Although the wheel speed is often ofinterest, that speed is not necessarily (or typically) the same asengine speed. Since engine speed is also of interest (for example, indetermining the timing of the closing of the exhaust valves 28 as willbe described further below), the electronic control circuitry 116further includes certain additional circuitry as shown. In particular,the electronic control circuitry 116 includes an engine speed sensor 678that measures the rate at which left and right latches 674 and 676(which can be considered steering or toggling latches) within theelectronic control circuitry are switching. As will be described furtherbelow with respect to FIG. 13, the switching of the states of theinternal latches 674, 676 is indicative of the frequency with whichcombustion events are occurring in the opposing combustion chambers 22of the cylinders 10 and 12 of the engine 4, and thus an indication ofengine speed. Although FIG. 12 in particular shows the electroniccontrol circuitry 116 as including two of the internal latches 674, 676,the actual number of latches can be greater, and in particular in atleast some embodiments the electronic control circuitry 116 will includea pair of latches for every pair of cylinders in the engine.

Additionally as shown, the electronic control circuitry 116 is coupledto each of the air tank 36, the main compressor 38, the auxiliarycompressor 40 and the battery 42, or more particularly, to sensorslocated at those devices, such that the electronic control circuitry isable to receive sensory signals indicative of the air pressure withinthe air tank 36, the operational status of the compressors 38 and 40,and the charging, voltage or other electrical status of the battery 42.Further, the electronic control circuitry 116 is coupled to numerouscontrollable devices and monitorable devices within the main portion 34of the engine 4, as well as within the auxiliary power unit 44. Moreparticularly as shown, the electronic control circuitry 116 is coupledto each of the respective sparking devices 24, intake valves 26, exhaustvalves 28, and fuel injectors 32 associated with each of the cylinders10-16 and 50, 52 of the main portion 34 of the engine 4 and theauxiliary power unit 44. Also, the electronic control circuitry 116 iscoupled to each of the electrodes/EOT sensors 154 associated with therespective dashpot assemblies 136 within each of those cylinders.Notwithstanding FIG. 12, depending upon the embodiment, the electroniccontrol circuitry 116 can also receive signals from other devices notshown, as well as provide control signals to other devices not shown.

Referring to FIG. 13, given the connections between the electroniccontrol circuitry 116 and other components as shown in FIG. 12, theelectronic control circuitry is able to control operation of the engine4 in accordance with a flow chart 600. The particular algorithmrepresented by FIG. 13 is intended to allow the electronic controlcircuitry 116 to operate the cylinders 10, 12 in any of the mannersdescribed above with respect to FIGS. 6A-11, and to allow switchingamong the different modes of operation described above in a seamlessmanner. Although intended for use particularly in controlling operationsrelating to the cylinders 10, 12 of the cylinder assembly 100 of themain portion 34 of the engine 4, the algorithm is equally applicablewith respect to controlling operations relating to the cylinders 14, 16of the main portion of the engine, as well as the cylinders 50, 52 ofthe auxiliary power unit 44, albeit it will be understood that it isseldom (if ever) the case that the cylinders of the auxiliary power unitwill operate in any of the abnormal modes of operation described abovein particular with respect to FIGS. 9-11.

As shown in FIG. 13, operation of the electronic control circuitry 116can conveniently be thought of as beginning when an operator hascommanded the engine 4 to be turned on, for example, when a signal isprovided to the electronic control circuitry 116 indicating that theignition switch 672 has been switched on, at a step 602. When such acommand has been received, the electronic control circuitry 116 next ata step 604 determines whether the air pressure provided by the air tank36 is too low. Typically this will not be the case. Assuming properdesign of the air tank 36, the air tank should be able to maintain agiven pressure level over a long period of time without leakage, and sothe air tank should still be at a previously-set pressure level evenafter the engine 4 has been dormant for a long period of time(typically, when the engine is shut off, the auxiliary power unitcontinues to operate, typically for a few seconds, until the air tank isat its appropriate pressure setting). Therefore, since typically the airtank 36 will have been pre-pressurized to a high enough level due tooperation of the engine at an earlier time, the air tank should normallybe at a desired pressure level upon beginning engine operation.

Nevertheless, if the air pressure within the air tank 36 is determinedto be too low at the step 604, then the electronic control circuitry 116activates either the electric air compressor 40 or the main aircompressor 38 (in which case the auxiliary power unit 44 is alsoactivated), at a step 606. More particularly, if the air pressure withinthe air tank 36 is insufficient to allow proper operation of theauxiliary power unit 44 and the main air compressor 38, then theelectric air compressor 40 is switched on (typically for a small airtank this will only take a few seconds). However, if the air pressurewithin the air tank 36 is sufficient to allow proper operation of theauxiliary power unit 44, or once the air pressure within the air tankbecomes sufficient to allow such operation of the auxiliary power unit(e.g., after preliminary operation by the electric air compressor 40),then the auxiliary power unit and the main air compressor 38 becomeoperational until the air tank 36 reaches the desired operationalpressure (this can take, for example, about 4-10 seconds). Once eitherof the compressors 40 and 38 is operational, the system returns to thestep 604. However, the electronic control circuitry 116 continues tocycle back and forth between the steps 604 and 606 until such time asthe air pressure is sufficiently high within the air tank 36. Typically,by the time that the air pressure within the air tank 36 is high enoughfor proper operation of the main portion 34 of the engine 4, theauxiliary power unit 44 is also operating.

Next, at a step 608, the electronic control circuitry 116 detectswhether the accelerator 670 has been depressed or otherwise a signal hasbeen provided indicating that the engine should be activated. If theanswer is no, then the system remains at step 608, and the main portion34 does not yet begin operation (that is, no combustion events occuryet). If the answer is yes, then the system next proceeds to a step 610.At the step 610, the electronic control circuitry 116 determines basedupon one or more signals received from the EOT sensors 154 whether agiven piston assembly (such as the piston assembly 67 described above)is positioned at one of the left or right EOT positions associated withits respective cylinder assembly, or alternatively is not at any EOTposition. As shown, if it is determined by the electronic controlcircuitry 116 that the piston assembly is located at a left EOT positionor is at neither of the EOT positions, then the electronic controlcircuitry proceeds to a step 612. Otherwise, if it is determined thatthe piston assembly is at the right EOT position, then the electroniccontrol circuitry 116 proceeds to a step 642. In alternate embodiments,if neither EOT position is achieved, instead of proceeding to the step612, the electronic control circuitry can instead proceed to the step642.

Further as shown, upon arriving at the step 612, the electronic controlcircuitry 116 sets (e.g., switches “on”) the left latch 674 and resets(e.g., switches “off”) the right latch 676, which as mentioned above areswitches that are part of the electronic control circuitry 116 (see FIG.12). The setting of the left latch 674 and resetting of the right latch676 cause the electronic control circuitry 116 to proceed withperforming a series of steps (e.g., steps 612-629) that result in acombustion event occurring at the first (left) cylinder 10. In contrast,upon arriving at the step 642, the electronic control circuitry 116instead resets (e.g., switches “off”) the left latch 674 and sets (e.g.,switches “on”) the right latch 676, which cause the electronic controlcircuitry 116 to proceed with performing a different series of steps(e.g., steps 642-659) that result in a combustion event occurring at thesecond (right) cylinder 10.

Assuming that the electronic control circuitry 116 has proceeded to thestep 612, as shown in FIG. 13 the electronic control circuitrysubsequently proceeds to perform each of steps 614, 616 and 620. Thestep 614, which is shown in dashed lines, represents an optionaloperation that can be performed in some implementations, and isdescribed further below (this step does not correspond to the manner ofoperation shown in the timing diagrams 8-11). Assuming that the step 614is not performed, the electronic control circuitry 116 advances from thestep 612 to the step 616, at which it provides a control signal to theleft exhaust valve 28 causing that valve to close, and to a step 620, atwhich it provides a control signal to the right exhaust valve causingthat valve to open. Thus, the steps 616 and 620 correspond to theactions shown in FIG. 8 at the times T₁ and T₂₁, in FIG. 9 at the timesT₁ and T₄₁, and in FIG. 11 at the times T₁ and T₉₁. Upon completion ofthe step 620, the electronic control circuitry 116 proceeds to a step621, at which it activates a left intake valve delay timer so as todelay further advancement of the process for an amount of timesufficient to allow the left exhaust valve 28 to close (e.g., withrespect to FIG. 8, the amount of time difference between the times T₁and T₂).

After the delay associated with the step 621 has passed, the electroniccontrol circuitry 116 then proceeds to steps 622 and 623, at which itprovides a left fuel injector signal and also activates a left fuelinjector pulse timer, respectively. Simultaneously with the steps 622and 623, the electronic control circuitry 116 also performs steps 624and 625, at which it provides a left intake valve signal and activates aleft intake valve pulse timer, respectively. The performing of the steps622 and 623 corresponds to the transitioning of the left fuel injectorgraph 210 at the time T₂, along with the continued maintaining of thathigh level signal until the time T₃, as shown in FIG. 8 (among otherplaces). The performing of the steps 624 and 625 corresponds to thetransitioning of the left intake valve graph 212 at the time T₂, alongwith the continued maintaining of that high level until the time T₄,also as shown in FIG. 8 (among other places). It will be noted that thelengths of each of the pulse timers employed in the steps 623 and 625 inthe present embodiment are determined by the electronic controlcircuitry 116 based upon the sensed position of the accelerator pedal670 as determined at the step 608. If the accelerator pedal 670 isdepressed more greatly, indicating the operator's desire for greaterengine power, the timers in the steps 622, 624 will adjust for a longerperiod of time calling for a greater injection of fuel and pressurizedair into the left combustion chamber 22.

Upon the completion of the steps 623 and 625 (it will be noted that thestep 623 usually completes earlier than the step 625), the electroniccontrol circuitry 116 then proceeds to a step 626, at which it activatesa firing delay timer that must be timed out prior to the firing of theleft sparking device 24. Activation of the timer in the step 626corresponds to the delay between times T₄ and T₅ as shown in thesparking delay graph 216 of FIG. 8 (among other places). Subsequent tothe step 626, the electronic control circuitry 116 then performs a step628, at which it activates a left sparking device pulse timer, andsubsequently a step 629, at which it provides a signal to actuate theleft sparking device 24. In addition to performing the steps 628 and629, simultaneously with those steps the electronic control circuitry116 further performs a step 630, at which the electronic controlcircuitry initiates a timeout timer. The left sparking device signalprovided at the step 629 causes the switching on of the left sparkingdevice 24, for example, at the time T₅ of FIG. 8 (among other places),while the expiration of the left sparking device pulse timer of the step628 results in the cessation of the left sparking device signal suchthat the left sparking device is switched off, for example at the timeT₆ shown in FIG. 8. Although not shown, in alternate embodiments it isalso possible for the left sparking device signal to take a form thatwill cause the left sparking device to produce multiple, repeated sparksover the period of time determined by the left sparking device pulsetimer (or over some other period of time, for example, during a periodof time up until an EOT condition or timeout condition occurs).

Subsequent to the performance of the steps 629 and 630, several thingshappen simultaneously. Upon the performance of the step 629 inparticular, at a step 632, it is determined whether the piston assemblyis no longer positioned at the left EOT position. Simultaneously, uponinitiating the timeout timer at the step 630, the electronic controlcircuitry 116 proceeds to a step 634 at which it continually revisitswhether the timeout timer has expired (in at least one embodiment, thetimeout timer is set to expire after 500 msec). The step 634 inparticular continues to be re-executed until the timeout timer expires,unless the electronic control circuitry 116 at the step 632 determinesthat the piston assembly is no longer at the left EOT position andfurther, at a step 661, determines that the piston assembly has reachedthe right EOT position. To the extent that the timeout timer expires atthe step 634 without the conditions of 632 and 661 being met, then theelectronic control circuitry 116 proceeds to a step 636, at which theelectronic control circuitry effectively makes a new determination ofwhether the piston assembly is located at either the left or right EOTpositions or at neither of those positions, as was originally determinedat the step 610.

If at the steps 632 and 661 it is determined that the piston assemblyhas migrated to the right EOT position, or if at the step 636 it isdetermined that the piston assembly is at the right EOT position, thenthe electronic control circuitry proceeds to the step 642. However, ifalternatively at the step 636 it is determined that the piston assemblyremains at the left EOT position, then the electronic control circuitry116 proceeds back to the step 612. Also, if at the step 636 it isdetermined that the piston assembly is currently at neither of the EOTpositions, then the electronic control circuitry 116 proceeds to a step638 at which it determines which of the right or left latches iscurrently set (as opposed to reset). If the right latch is currently set(and correspondingly the left latch is currently reset), then the systemreturns to the step 612. Alternatively, if the left latch is currentlyset (and the right latch is currently reset), then the system proceedsto the step 642 instead.

If the electronic control circuitry 116 arrives at the step 642, eitherfrom the step 610 or alternatively from any of the steps 636, 638 or661, it has arrived there either because the piston assembly 67 is atthe right EOT position (as determined at the steps 610, 636 or 661) oralternatively because the piston assembly is in between the EOTpositions but the left latch is currently set (as determined at the step638). As mentioned above, upon arriving at the step 642, the electroniccontrol circuitry 116 sets the right latch 676 and resets the left latch674, and then proceeds to perform each of steps 644, 646 and 650. Aswith respect to the step 614, the step 644, which is shown in dashedlines, represents an optional operation that can be performed in someimplementations, and is described further below (this step does notcorrespond to the manner of operation shown in the timing diagrams8-11). Assuming that the step 644 is not performed, the electroniccontrol circuitry 116 advances from the step 642 to the step 646, atwhich it provides a control signal to the right exhaust valve 28 causingthat valve to close, and to a step 650, at which it provides a controlsignal to the left exhaust valve causing that valve to open. Uponcompletion of the step 650, the electronic control circuitry 116proceeds to a step 651, at which it activates a right intake valve delaytimer so as to delay further advancement of the process for an amount oftime sufficient to allow the left exhaust valve 28 to close (e.g., withrespect to FIG. 8, the amount of time difference between the times T₁₁and T₁₂).

After the delay associated with the step 651 has passed, the electroniccontrol circuitry 116 then proceeds to steps 652 and 653, at which itprovides a right fuel injector signal and also activates a right fuelinjector pulse timer, respectively. Simultaneously with the steps 652and 653, the electronic control circuitry 116 also performs steps 654and 655, at which it provides a right intake valve signal and activatesa right intake valve pulse timer, respectively. The performing of thesteps 652 and 653 corresponds to the transitioning of the right fuelinjector graph 220 at the time T₁₂, along with the continued maintainingof that high level signal until the time T₁₃, as shown in FIG. 8 (amongother places). The performing of the steps 654 and 655 corresponds tothe transitioning of the right intake valve graph 222 at the time T₁₂,along with the continued maintaining of that high level until the timeT₁₄, also as shown in FIG. 8 (among other places). As with the pulsetimes employed in the steps 623 and 625, the lengths of each of thepulse timers employed in the steps 653 and 655 in the present embodimentare determined by the electronic control circuitry 116 based upon thesensed position of the accelerator pedal 670 as determined at the step608.

Upon the completion of the steps 653 and 655 (it will be noted that thestep 653 usually completes earlier than the step 655), the electroniccontrol circuitry 116 then proceeds to a step 656, at which it activatesa firing delay timer that must be timed out prior to the firing of theright sparking device 24. Activation of the timer in the step 656corresponds to the delay between times T₁₄ and T₁₅ as shown in thesparking delay graph 216 of FIG. 8 (among other places). Subsequent tothe step 656, the electronic control circuitry 116 then performs a step658, at which it activates a right sparking device pulse timer, andsubsequently a step 659, at which it provides a signal to actuate theright sparking device 24. In addition to performing the steps 658 and659, simultaneously with those steps the electronic control circuitry116 again also performs the step 630, at which the electronic controlcircuitry initiates the timeout timer. The left sparking device signalprovided at the step 659 causes the switching on of the right sparkingdevice 24, for example, at the time T₁₅ of FIG. 8 (among other places),while the expiration of the right sparking device pulse timer of thestep 658 results in the cessation of the right sparking device signalsuch that the right sparking device is switched off, for example at thetime T₁₆ shown in FIG. 8.

As was the case subsequent to the performance of the steps 629 and 630described above, several things also happen simultaneously subsequent tothe performance of the steps 659 and 630. Upon the completion of thestep 659 in particular, it is determined at a step 660 whether thepiston assembly is no longer at the right EOT position. If the pistonassembly still is at the right EOT position, the electronic controlcircuitry 116 remains at the step 660 while, if it has left the rightEOT position, then the electronic control circuitry proceeds to a step640, at which it is determined whether the piston assembly has reachedthe left EOT position. At the same time, while one or both of the steps660 and 640 are being performed, the electronic control circuitry 116also performs the step 634 in which it determines whether the timeouttimer has expired.

If the electronic control circuitry 116 determines at the step 634 thatthe timeout timer has expired prior to determining that the pistonassembly has both left the right EOT position at the step 660 andreached the left EOT position as determined at the step 640, then theelectronic control circuitry proceeds from the step 634 to the step 636,at which it makes a new determination of the piston assembly position asdescribed above. If, however, the requirements of the steps 660 and 640are determined by the electronic control circuitry 116 to have been metprior to the expiration of the timeout timer of the step 634, then theelectronic control circuitry returns to the step 612. In this manner,then, the electronic control circuitry 116 can cycle back to either thestep 612 or the step 642 depending upon whether the piston assembly isdetermined as being at one of the left or right EOT positions, or inbetween those EOT positions.

FIG. 13 is intended particularly to show exemplary operation of theelectronic control circuitry 116 in relation to one of the cylinderassemblies of the main portion 34 of the engine 4, namely, the cylinderassembly 100 with its cylinders 10 and 12 described above. From theabove description, it should be particularly evident that, when theelectronic control circuitry 116 operates in accordance with FIG. 13 (aswell as when the engine operates in accordance with any of the timingdiagrams of FIGS. 8-11), the electronic control circuitry 116 typicallyalternates, in a repeated manner, between operation in which the leftlatch 674 is set and combustion occurs in the left cylinder 10, andoperation in which the right latch 676 is set and combustion occurs inthe right cylinder 12. Thus, it should further be evident that, bymonitoring the rate of switching of the states of the latches 674, 676,the engine speed sensor 678 is able to obtain a measure of the speed ofoperation of the engine, or at least the speed of operation of thecylinder assembly 100.

Such engine speed information can be particularly useful in certainembodiments (particularly embodiments differing somewhat from thatdescribed above), for example, embodiments in which the steps 614 and644 mentioned above are performed. More particularly in this regard, itis not always desirable that the exhaust valves 28 be actuated (so as tobe closed) immediately upon the piston assembly attaining one of the EOTpositions as discussed above. In some circumstances, even though thepiston assembly has attained one of the EOT positions (e.g., the leftEOT position), it is nevertheless not desirable to immediately close thecorresponding exhaust valve (e.g., the left exhaust valve) since suchclosure of the exhaust valve can prematurely limit the ability of thepiston assembly to continue moving in the direction it was traveling(e.g., the left direction) due to pressure changes within its associatedcombustion chamber. This is particularly the case as the speed of theengine is reduced.

In such circumstances it can be desirable therefore to introduce a delaybetween the time at which the piston assembly reaches a given EOTposition and the time at which the corresponding exhaust valve isclosed. Further, it often is desirable that the amount of time delayshould take into account engine speed, and particularly that the amountof time delay be increased as the engine speed is decreased, andvice-versa. Assuming this to be the case, therefore, the respectivesteps 614 and 644 of FIG. 13 can be implemented, between the steps 612and 616 and the steps 642 and 646, respectively, to introduce such adelay. More particularly, the step 614 involves providing a variableclosing delay to the left exhaust valve, and thereby delays theperformance of the step 616 relative to the step 612, while the step 644involves providing a variable closing delay to the right exhaust valve,and thereby delays the performance of the step 646 relative to the step642. Further as shown, in each case, the providing of the variableclosing delays is based upon received detected engine speed information,which is represented as being received at a step 618.

Although FIG. 13 for simplicity shows operation of the electroniccontrol circuitry 116 as it pertains particularly to the cylinderassembly 100, it will further be understood that, insofar as the mainportion 34 of the engine 4 of FIG. 2 includes two cylinder assembliescomprising two different pairs of cylinder 10, 12 and 14, 16,respectively, the electronic control circuitry 116 for this enginetypically will perform, simultaneously, at least two such algorithms asthat shown in FIG. 13, one with respect to each of the two differentassemblies. In at least some such embodiments, the electronic controlcircuitry 116 will include another set of latches in addition to thelatches 674, 676, as well as possibly another engine speed sensor inaddition to the sensor 678, in order to detect the speed of operationassociated with the cylinders 14 and 16. Also, insofar as it istypically desirable for the cylinder assembly 100 including thecylinders 10 and 12 to be operated in a manner that is opposite that ofthe cylinder assembly including the cylinders 14 and 16 so as to achieveengine balancing (and thereby achieve engine operation with lessundesirable vibrations), the electronic control circuitry 116 in atleast some embodiments will coordinate its operation in relation to thecylinders 10, 12 with its operation in relation to the cylinders 14, 16so as to achieve such balanced operation.

Although not shown in FIG. 13, it should further be noted that,typically, it is desirable for the engine 4 to begin operation with itspiston assemblies (e.g., the piston assembly 67) being located at EOTpositions rather than somewhere in between EOT positions. This isdesirable particularly since, if the piston assemblies are in suchconditions at the commencement of engine operation, the pistonassemblies therefore are ready to perform combustion events that willprovide the most initial force. Typically, additional efforts will notneed to be exerted for the piston assemblies to arrive at the EOTpositions, insofar as the piston assemblies naturally tend to end up attheir EOT positions (e.g., when the piston assemblies are successfullybeing operated in the manner described with respect to FIG. 8).

Turning to FIG. 14, an additional schematic diagram 680 illustratesportions of an alternate embodiment of the engine 4 in which thecylinders 10, 12, 14 and 16 are hydraulically coupled not merely to thehydraulic motor 18 but also are coupled to additional components bywhich the engine is capable of providing regenerative brakingfunctionality. As shown, the cylinders 10, 12, 14 and 16 have the samecomponents and arrangement as shown in FIG. 3. That is, each of thecylinders 10, 12, 14 and 16 includes a respective combustion chamber 22,a respective hydraulic chamber 64, and a respective piston 62. Further,the pistons 62 of the cylinders 10 and 12 are linked by way of theconnector tube 66 and the pistons of the cylinders 14 and 16 are linkedby way of the connector tube 68. Additionally, check valves 72 and 74are respectively coupled between the hydraulic chamber 64 of the firstand second cylinders 10, 12 and links 94, by which those cylinders areconnected to a reservoir, which in the present embodiment is shown as areservoir 690. Further, the check valves 76 and 78 also linked to thoserespective hydraulic chambers 64 of the cylinders 10, 12 are linked tothe check valves 82 and 84 by way of links 80, with the check valves 82and 84 being respectively coupled to the hydraulic chambers 64 of thecylinders 14 and 16, respectively. Additionally, the further checkvalves 86 and 88 also are coupled to the hydraulic chambers 64 of thecylinders 14 and 16, respectively, are each coupled by way of links 90to one another and to the hydraulic wheel motor 18, which can be avariable displacement hydraulic wheel motor.

As shown, in this embodiment, the hydraulic wheel motor 18 is notdirectly coupled back to the reservoir 690, but rather is coupled by wayof a link 696 to the input terminal of a three-way, two-positionproportional hydraulic valve, which can also be referred to as a brakingvalve 682. Typically the braking valve 682 is operated by way of asingle solenoid (which can be controlled by the electronic controlcircuitry 116 described above), with a spring return, but it also can bepilot-operated. One of two selectable output terminals of the brakingvalve 682 (opposite the terminal connected to the link 696) is connectedto the reservoir 690 by way of a link 684 such that, when the brakingvalve 682 is in the position shown in FIG. 14, hydraulic fluid passingthrough the hydraulic motor 18 returns to the reservoir 690 by way ofthe link 684. However, the other of the two selectable output terminalsof the braking valve 682 is also connected, by way of links 688, to anaccumulator 692. The accumulator 692 is further coupled, by way of links689, to an additional re-acceleration valve 686, which in the presentembodiment is a two-way, two-position proportional hydraulic valve. There-acceleration valve 686 additionally is coupled between the links 689and an additional link 694 that merge (e.g., is coupled to) the links 90and thus is coupled to the hydraulic wheel motor 18.

Given the above-described arrangement, hydraulic fluid flow between thelinks 689 and 694 is prevented when the re-acceleration valve 686 is ina closed position (closed to fluid flow) as shown in FIG. 14. Thus,hydraulic fluid flow between the accumulator 692 (as well as the links688) and the links 694 is also prevented when the re-acceleration valve686 is closed. However, when the re-acceleration valve 686 is shifted(again by solenoid operation) to an open position so as to couple thelinks 689 and 694, hydraulic fluid can flow from the hydraulicaccumulator 692 to the links 694 and thus to the hydraulic wheel motor18 by way of the links 90.

The engine represented by the schematic diagram 680 operates as follows,when implemented in a vehicle such as that of FIG. 1. When the engine isoperating (and combustion events are occurring within the enginecylinders) to drive hydraulic fluid toward the hydraulic wheel motor 18in response to an operator's depressing of the accelerator pedal 670,the braking valve 682 directs the hydraulic fluid flow to the reservoir690. At this time, hydraulic fluid is not allowed to proceed to theaccumulator 692 since, if fluid was directed in that manner, fluid wouldaccumulate in the accumulator and eventually the engine pistons wouldcease operating properly. Further, when the vehicle is moving (or thehydraulic wheel motor 18 is otherwise rotating) but the acceleratorpedal 670 is released, hydraulic fluid continues to flow from thereservoir 690 through the engine check valves 72-78 and 82-88, throughthe hydraulic wheel motor 18 and back to the reservoir, even though theengine itself stops running whenever the accelerator is released (e.g.,even though combustion events driving the pistons 62 no longer areoccurring). In this operational state, the engine is free-wheeling.

However, when a brake is depressed by an operator (again, as sensed bythe electronic control circuitry 116), the free-wheeling flow throughthe hydraulic wheel motor 18 is diverted away from the reservoir 690 andinstead sent to the accumulator 692. More particularly, this occursbecause the electronic control circuitry 116 actuates the solenoid ofthe braking valve 682 to move away from the position shown in FIG. 14towards a position in which hydraulic fluid flow is directed from thelinks 696 to the links 688 and thus to the accumulator 692 rather thanto the links 684. When this occurs, typically the re-acceleration valve686 is in the closed position shown, that is, precluding the flow offluid between the links 689 and the links 694. Consequently, the fluidis diverted into the hydraulic accumulator 692 causing the pressuretherein to rise. As noted above, the braking valve 682 in the presentembodiment is a proportional valve, such that the volume of fluid beingredirected to the accumulator 692 at any given time need not include allof the fluid proceeding through the links 696 away from the hydraulicwheel motor 18. Further, the operation of the braking valve 682 can bemodulated to ensure a smooth and appropriate braking function, basedupon the amount of fluid/pressure in the accumulator 692.

Once the brake pedal is released, the braking valve 682 is controlled toreturn to its normal position in which hydraulic fluid is completelydirected back to the reservoir 690. This also occurs if the accumulator692 becomes filled, as there must be a place for hydraulic fluid to flowin this circumstance. Also, if the hydraulic accumulator 692 becomescompletely filled, or if more aggressive braking is desired by theoperator than can be achieved by diverting flow to the hydraulicaccumulator by way of the regenerative braking system, then theelectronic control circuitry 116 can cause normal braking (e.g., by wayof brake pads interacting with wheels of the vehicle). When the vehicleis completely stopped, the braking valve 682 also returns to the normalposition as shown.

When hydraulic fluid/pressure is accumulated within the hydraulicaccumulator 692, it is possible to drive the hydraulic motor 18 withsuch fluid/pressure. In particular, when such pressure exists within thehydraulic accumulator 692, and the accelerator pedal 670 of the vehicleis depressed by the operator, the re-acceleration valve 686 is energizedso as to shift from the normal, closed position shown in FIG. 14 to anopen position such that hydraulic fluid can flow from the hydraulicaccumulator 692 via the links 689 to the links 694, 90 and thereby tothe hydraulic wheel motor 18. During this manner of operation, thebraking valve 682 is maintained in its normal position such that allfluid is directed back to the reservoir 690. So that the reservoir canaccommodate the increased volume of fluid that can be accumulated by theaccumulator 692 during braking, the reservoir typically will be largerthan the reservoir 70 of FIG. 3. It should be noted that the hydraulicfluid proceeding out of the re-acceleration valve 686 via the links 694does not proceed into the hydraulic chambers 64 of the cylinders 14, 16,since the check valves 86 and 88 preclude such flow. The re-accelerationvalve 686, as described above, is also of the proportional type, suchthat the electronic control circuitry 116 based upon the setting of theaccelerator pedal 670 can smoothly control vehicle acceleration bymodulating the rate of fluid output drawn from the accumulator 692.

It is typically the case that the engine will not be running (e.g., thecylinders 10-16 will not be experiencing combustion events) when thehydraulic wheel motor 18 is being driven by hydraulic fluid from theaccumulator 692. Nevertheless, in some circumstances, it is possiblethat the hydraulic fluid driving the hydraulic wheel motor 18 will beprovided to the motor from both the accumulator 692 and from thecylinders 10-16. In any event, once the pressure within the hydraulicaccumulator 692 drops to a point where it can no longer sustain desiredvehicle acceleration/speed, the engine begins running (again, that is,the cylinders 10-16 experience combustion events) such that hydraulicfluid is supplied to the hydraulic wheel motor by way of the links 90.At this point, the re-acceleration valve 686 is de-energized, and theregenerative braking system is effectively inactivated until the nextbraking event occurs.

Embodiments of the present invention including one or more of thosedescribed above are advantageous relative to conventional internalcombustion engines in one or more regards. First, embodiments of thepresent inventive engine are fully capable of commencing operation, andcontinuing operation, without any starter (e.g., a battery drivenelectrical motor) or any flywheel (or other device for maintainingmomentum). Conventional engines that employ a crankshaft driven by oneor more pistons typically require a starter because the force derivedfrom any given combustion stroke(s) of any given piston(s) isinsufficient to rotate the crankshaft and move its associated piston(s)sufficiently far that the position(s) of those piston(s) are appropriatefor additional combustion stroke(s) to occur. Rather, during thestarting process, before or after one or more combustion stroke(s) haveoccurred, the engine components can shift to a “dead” position in whichit is not yet appropriate for any further combustion stroke(s) to occur.The existence of such dead positions particularly occurs because, inbetween successive combustion strokes, it is necessary to performcompression strokes that both take time and sap rotational momentum fromthe system. Because of the existence of these dead positions, it isnecessary for an outside force (e.g., the starter) to further move theengine components beyond these positions to different positions in whichit is appropriate for further combustion stroke(s) to occur

In contrast, because embodiments of engines in accordance with thepresent invention employ pairs of aligned, oppositely-directed pistons,and because these embodiments receive compressed air from the air tankrather than perform any compression strokes to generate compressed air,these engines and their piston assemblies never move to or become stuckat dead positions. Rather, because at any time a new supply ofcompressed air (and fuel) can be provided to any given combustionchamber without the performance of any compression stroke, it is alwayspossible to cause another combustion event to occur with respect to agiven piston assembly, no matter what the position of the pistonassembly happens to be. Additionally, because embodiments of the presentinvention employ pairs of aligned, oppositely-directed positions, everycombustion stroke tends to drive the piston assembly directly toward aposition at which it is appropriate to cause a combustion strokedirected in the opposite direction. That is, operation of the enginenaturally drives the piston assemblies in such a manner that, after anygiven combustion stroke, the piston assembly is reset to a position thatis appropriate for another combustion stroke to take place.

At the same time, even if a given combustion event in a given combustionchamber of a cylinder assembly fails to drive the piston assemblysufficiently far so as to move the piston assembly to a position whereit is appropriate for the next combustion event to be performed in theother combustion chamber of the cylinder assembly (e.g., the pistonassembly remains at a given EOT position as shown in FIG. 11),additional combustion strokes can still be performed repeatedly in thesame combustion chamber (again as shown in FIG. 11). Again, this isbecause, regardless of the piston assembly position, compressed air (andfuel) sufficient for enabling a combustion stroke can always be inductedinto any combustion chamber associated with any given cylinder assemblyof the engine at any given time. Thus, every combustion event withinthese embodiments of the present invention tends to positively directthe engine toward a state, or at least leaves the engine in a state, inwhich a further combustion event is possible and appropriate.

Given these considerations, no starter (e.g., electric starter,pneumatic starter, hydraulic starter, hand crank starter or otherstarting means or structure for performing a starting function) isrequired by at least some embodiments of the present invention in orderto allow the engine to begin operating, that is, no starter is requiredby these embodiments to allow combustion events within the engine tobegin occurring and continue occurring in a sustainable or steady-statemanner. Regardless of whether or when the last combustion event in theengine has occurred, or how long the engine has been “off”, the engineis always ready to begin performing combustion events in response to anoperator signal (e.g., depressing of an accelerator) or otherwise.Operation of the engine is always either in an “on” state wherecombustion events are occurring (with high levels of force/torque), orin an “off” state where combustion events are not occurring, but neverin a “start” state where a separate, starter mechanism is helping todrive the engine so that it can attain a steady “on” state of operation.

It should further be mentioned that, because no starter is required,such embodiments of engines are capable of operating or running (thatis, experiencing successive combustion events) at a variety of speeds,and in particular are capable of running at very low speeds (includingat zero speed and near-zero speeds) that would be unstable for manyconventional four stroke and two stroke crankshaft-based engines.Further, in embodiments in which regenerative braking is employed (suchas that described in FIG. 14), it is further possible to achieve initialoutput momentum without even beginning operation of the engine (that is,without the occurrence of any combustion events), simply by directingsome of the stored fluidic energy within the accumulator to thehydraulic wheel motor (or other output device).

The fact that embodiments of the present invention have no need for astarter goes hand-in-hand with the additional attribute that embodimentsof the present invention have no need for a flywheel. In conventionalengines involving a crankshaft, whether those engines are four stroke ortwo stroke engines, it is typically necessary to employ a flywheel sothat sufficient rotational momentum of the crankshaft can be maintainedto overcome the resistive force that is generated within the enginesafter a given combustion event has occurred and the piston(s) of theengine are only serving to compress and/or exhaust contents within theircombustion chambers, so as to allow the engine to return to a state atwhich further combustion event(s) can occur.

By comparison, and as already discussed, embodiments of the presentinvention employing pairs of aligned, oppositely-directed pistons neverface a situation in which further combustion event(s) cannot beperformed. Rather, no matter what the position of a given pistonassembly, it is always possible to cause an additional combustion eventto occur in one (or possibly either) of its associated combustionchambers. Further, because the vehicle (or other load) itself can serveas a flywheel due to inertia, the vehicle itself can serve to balance orsmooth out any variations in torque, pressure and/or volumetric fluidflow that occur as combustion events occur, pass, and then are repeated.Thus, even though no engine flywheel is present in the above-describedembodiments, noticeable variations in vehicle velocity normally stillwill not occur due to the alternation of combustion events followed bythe absence of such events.

Equally if not more significantly, the vehicle movement and associatedmomentum serves also to provide a phenomenon that can be referred to as“thermodynamic freewheeling” behavior. Such behavior occurs particularlywhen pistons are able to fully complete their travel down the entirelengths of their cylinder bores during combustion strokes (prior to theexhaust strokes) while continuing to perform net work throughout thosemovements, which in turn maximizes energy output of the engine (that is,all possible heat energy from each combustion stroke is squeezed out ofthe engine and available for performing work). Due to the “thermodynamicfreewheeling” behavior provided by the engine, fuel efficiency isfurther enhanced. It should further be noted that inclusion of anaccumulator (or other source of backpressure) within the hydrauliccircuit formed from the engine's hydraulic cylinders, hydraulic wheelmotor and reservoir would tend to negate this benefit (albeit use of anaccumulator as described above in connection with regenerative braking,where the accumulator is separate from the hydraulic circuit formed fromthe engine cylinders, wheel motor and reservoir, does not entail thissame difficulty).

Embodiments of the present invention further are advantageous bycomparison with many conventional engines given their arrangement ofaligned, oppositely-directed pistons that are operated in a 2 strokemanner in terms of the amount of torque that can be generated by theseembodiments. In a conventional 4 stroke engine employing a crankshaft,force and corresponding torque are generated by a given piston only onceevery four times it moves. In contrast, embodiments of the presentinvention such as those described above employ pistons 62 that, giventheir 2 stroke manner of operation, generate force and correspondingtorque once every two times the piston moves. Further, because each ofthe pistons 62 of a given piston assembly such as the piston assembly 67is linked to and aligned with a complementary, oppositely-directedpiston, each piston assembly generates force and corresponding torquewith every single movement of that piston assembly.

Additionally, because embodiments of the present invention such as thosedescribed above produce torque by way of hydraulic fluid movement ratherthan by way of driving a crankshaft, the torque generating capability ofthese embodiments is further enhanced relative to engines withcrankshafts. In particular, while engines with crankshafts are only ableto achieve varying levels of torque as the angles of the connecting rodslinking the pistons of such engines with the crankpins of the crankshaftvary, the embodiments of the present invention never experience any suchtorque variation since movements of the pistons are converted intorotational movement by way of hydraulic fluid rather than by way of anymechanical linkages. Further, while engines with crankshafts are oftenunable to achieve significant or desired levels of torque immediatelywhen combustion events occur due to the particular angular positioningof the connecting rods (e.g., when a piston is at a “top dead center”position), embodiments of the present invention are always immediatelycapable of generating torque upon the occurrence of a combustion eventsince the force resulting from the combustion event is equally able tobe converted into torque by way of hydraulic fluid movement regardlessof piston position. Indeed, for all of these reasons, it is envisionedthat certain embodiments of the present invention may be able to outputtwo times or even three times the overall net torque generated by acomparable-weight 4 stroke crankshaft-based internal combustion engine.

Additionally, particularly insofar as embodiments of the presentinvention are capable of generating superior levels of torque, at leastsome embodiments of the present invention are able to drive the wheelsof a vehicle (or other load) directly as shown in FIG. 2, without anyintermediary devices being employed for the purpose of torqueconversion. In particular, while many conventional crankshaft-basedinternal combustion engines need to employ (or desirably employ)transmissions and/or differential gear (and/or running gear)arrangements by which engine output torque levels are converted intodesired torque levels at the wheels of the vehicle (or other outputdevices), at least some (if not all) embodiments of the presentinvention are capable of delivering desired torque levels to the wheels(or other output devices) entirely without any such transmissions orgear arrangements. In such embodiments, it is possible to achieveadditional torque multiplications (e.g., about four times the amount oftorque) simply by way of the variable displacement hydraulic wheel motor18.

In addition to generating superior levels of torque, at least someembodiments of the present invention are able to operate at asignificantly higher level of efficiency than many if not allconventional internal combustion engines. One reason for this is thatthe embodiments of the present invention are able to achieve asignificantly higher compression ratio (or “expansion ratio”) than manyconventional engines, where the compression ratio is understood as theratio of the largest, expanded volume of the combustion chambers of theengine cylinders (e.g., at a “bottom dead center” position at the end ofthe combustion stroke), to the smallest, reduced volume of thosecombustion chambers (e.g., at a “top dead center” position just prior tocombustion). More particularly, in many conventional 4 stroke,crankshaft-driven engines, the compression ratio is somewhat limited(e.g., to a factor of 9 or 10) due to the geometry of the enginecylinders, crankshaft, pistons, and connecting rods linking thosepistons to the crankshaft, which produce a risk of pre-ignition withhigh compression ratios.

In contrast, embodiments of the present invention can attain a highercompression (expansion) ratio (e.g., a factor greater than 14, forexample, a factor of 21 or even higher), and thus attain higher fuelefficiencies (e.g., about 17% to 21% higher fuel efficiencies) for thatreason. The configuration of these embodiments of engines entails areduced risk of pre-ignition, such that it is not necessary to alwaysutilize high octane fuel, and rather it is possible to utilize arelatively lower grade, lower octane (e.g., 80 octane) fuel. It shouldbe further noted that this ratio in relation to embodiments of thepresent invention is more aptly termed an “expansion ratio” rather thana “compression ratio” since no compression strokes are performed inthese embodiments (again, compressed air is supplied from the air tankinstead).

Embodiments of engines in accordance with the present invention providegreater fuel efficiency than many conventional engines for additionalreasons as well besides their greater compression (expansion) ratios.First, as already discussed above, embodiments of the present inventiondo not (or do not need to) employ any crankshaft or connecting rods,camshafts or associated components (e.g., timing chains), orconventional valve train components, and also can be implemented withoutany transmissions, differential gears, running gears, or othercomponents that are often employed to enhance torque output. Given theabsence of these components, embodiments of the present inventive enginecan be significantly lighter in weight relative to conventional enginesthat employ such components, and consequently can be more fuel efficientfor this reason.

Additionally as discussed above, embodiments of engines in accordancewith the present invention can begin operation (begin performingrepeated combustion events) without any starter. Thus such engineembodiments can start and stop operation immediately at will without anysignificant delay, and also are capable of delivering torque even in theabsence of any movement (e.g., at zero speed), similar to the behaviorof an electric vehicle (e.g., a golf cart). When a vehicle implementingsuch an engine is at a standstill or is coasting, the engine need not beon or operational at all (that is, no combustion events need be takingplace). Consequently, engine embodiments of the present invention neednot operate the engine in any low or idling mode where combustion eventsare occurring even though the power generated as a result of thosecombustion events is wasted. Thus, engine embodiments of the presentinvention can save all of the energy that is otherwise wasted duringidling operation by conventional engines during standstill or coastingoperation of the vehicle, which can be significant (e.g., a 20% energysavings). Further, as described above, at least some embodiments of thepresent invention can also employ regenerative braking techniques, whichfurther can save on energy that otherwise would be wasted when thevehicle is braked in a conventional manner with brake pads.

It should further be noted that embodiments of the present inventionfurther are advantageous relative to electric cars and hybrid vehicles(that employ both internal combustion engines and electric powersystems). Although (as discussed above) embodiments of the presentinvention share certain operational characteristics with electric cars,the embodiments of the present invention do not require the same batterypower levels that are required by such cars, and consequently do nothave the weight associated with the batteries used to provide suchbattery power. Further, while at least some embodiments of the presentinvention are capable of operating in a regenerative manner, which helpsto conserve power, unlike conventional hybrid vehicles these embodimentsdo not require two complicated power systems (e.g., involving both aninternal combustion engine and a complicated electric system includingan electric motor). Thus, such embodiments of the present invention areless complicated than hybrid vehicles.

Notwithstanding the above description, the present invention is intendedto encompass numerous other embodiments that employ one or more of thefeatures and/or techniques described herein, and/or employ one or morefeatures and/or techniques that differ from those described above. Forexample, while the above-described embodiments envision the use ofconventional hydraulic fluid such as oil within the hydraulic chambers64 of the cylinders and other engine components, in alternateembodiments other fluids can be utilized. For example, in someembodiments, water and/or a water-based compound can be used as thehydraulic fluid within the engine. Also, while the above-describedengine embodiments generate rotational power by driving hydraulic fluidthrough a hydraulic wheel motor (e.g., a motor that generates rotationaloutput), in alternate embodiments it would be possible to generatelinear output power. Additionally, while the above-described engineembodiments employ capacitance sensors (e.g., as formed using thedashpot assemblies 136 with their capacitor cases 138, and the connectortube collars 134), in other embodiments other types of position/motionsensor can be employed, such as magnetic sensors, magnetoresistivesensors, optical sensors, inductive proximity sensors and/or other typesof proximity sensors.

Further, while the above-described cylinder assemblies and pistonassemblies envision the use of pairs of aligned, oppositely-directedpistons, in alternate embodiments it would be possible to utilize agroup of pistons that, though oppositely (or substantially oppositely)directed, were not aligned with one another but rather were staggered inposition relative to one another (e.g., the pistons travel along axesthat are parallel with, but out of alignment with or offset from, oneanother). Additionally, various embodiments of the present inventiveengine designs can be employed with a variety of vehicles, for example,various two-wheel drive vehicles (with front wheels driven or rearwheels driven), vehicles with limited slip mechanisms, four-wheel drivevehicles, and others. In some embodiments, for example, in a front-wheeldrive vehicle, the engine can be implemented in such a manner that nohoses are needed to couple the engine housing to the hydraulic wheelmotor.

Also, in some embodiments, more than one EOT sensor or other positionsensor can be provided in any given cylinder to allow detection ofmultiple positional locations of the piston/piston assembly, as well asinformation that can be derived from such sensed location informationincluding, for example, velocity and/or acceleration. Additionally, insome alternate embodiments, two of the four check valves coupled betweenthe two pairs of cylinders (e.g., either the check valves 76 and 78, orthe check valves 82 and 84 of FIG. 3) are eliminated. For beneficialoperation of the engine without those two check valves, the two pistonassemblies should be operated so that the first piston assembly issubstantially exactly timed to move directly opposite to the movementsof the second piston assembly. Also, in some embodiments (orcircumstances) it is advantageous to only operate one of the twopiston/cylinder assemblies of the engine (e.g., only cause combustionevents to occur in one of the two piston assemblies, e.g., within thecombustion chambers 22 of the cylinders 10 and 12). This can bedesirable, for example, for fuel savings. Also, in some embodiments, thenumber of pistons, piston assemblies, cylinders and cylinder assembliesin the engine (and/or the auxiliary power unit) can vary from thatdescribe above.

Further, while the above-described embodiments envision implementationin vehicles and the like, embodiments of the present inventive enginecan also be employed in other devices that require rotational outputpower or other types of output power and, indeed, can be utilized todrive other energy conversion devices, such as electric generators.Additionally, while various advantages associated with certainembodiments of the present invention are discussed above, the presentinvention is intended to encompass numerous embodiments that achieveonly some (or none) of these advantages, and/or achieve otheradvantages.

It is specifically intended that the present invention not be limited tothe embodiments and illustrations contained herein, but include modifiedforms of those embodiments including portions of the embodiments andcombinations of elements of different embodiments as come within thescope of the following claims.

We claim:
 1. An internal combustion engine comprising: first and secondcylinders having first and second hydraulic chambers, respectively,first and second combustion chambers, respectively, and first and secondintake valves, respectively, the intake valves being capable ofgoverning flow into the respective combustion chambers; first and secondpistons positioned within the first and second cylinders, respectively,the first and second pistons being rigidly coupled to one another in amanner such that the pistons are substantially aligned with one anotherand oppositely-directed relative to one another; third and fourthcylinders having third and fourth hydraulic chambers, respectively,third and fourth combustion chambers, respectively, and third and fourthintake valves, respectively, the intake valves being capable ofgoverning flow into the respective combustion chambers; third and fourthpistons positioned within the third and fourth cylinders, respectively,the third and fourth pistons being coupled to one another in a mannersuch that the pistons are substantially aligned with one another andoppositely-directed, at least one hydraulic link at least indirectlyconnecting each of the first, second, third, and fourth hydraulicchambers with a hydraulic motor so as to convey hydraulic fluid drivenfrom the first, second, third, and fourth hydraulic chambers,respectively, by the first, second, third, and fourth pistons,respectively, to the hydraulic motor; and at least one source ofcompressed air that is linked at least indirectly to the combustionchambers by way of the respective intake valves, the compressed airbeing provided to the combustion chambers in anticipation of combustionstrokes, whereby, due to the providing of the compressed air from the atleast one source, the pistons need not perform any compression strokesin order for combustion events to occur therewithin.
 2. The internalcombustion engine of claim 1, wherein the first, second, third, andfourth cylinders respectively have first, second, third, and fourthexhaust valves, respectively, and first, second, third, and fourthsparking devices, respectively.
 3. The internal combustion engine ofclaim 2, wherein the first, second, third, and fourth intake valves arerespectively coupled at least indirectly to both the at least one sourceand to first, second, third, and fourth fuel injectors, respectively. 4.The internal combustion engine of claim 1, wherein the at least onesource is a pressurized air tank.
 5. The internal combustion engine ofclaim 1, wherein the first and second pistons are at least one of:aligned coaxially along a cylinder axis extending through each of thefirst and second cylinders; and offset from one another in a directionperpendicular to directions of travel of the pistons within thecylinders, such that the directions of travel of the pistons areparallel but axes along which the pistons travel are out of alignment.6. The internal combustion engine of claim 1, wherein first and secondcheck valves associated with the first and second hydraulic chambers,respectively, are coupled between those chambers and an intermediaryhydraulic link, wherein third and fourth check valves associated withthe third and fourth hydraulic chambers, respectively, are also coupledbetween those chambers and the intermediary hydraulic link, wherein theintermediary link and the check valves are respectively configured toallow hydraulic fluid to only flow from each of the first and secondhydraulic chambers to each of the third and fourth hydraulic chambers.7. The internal combustion engine of claim 6, wherein fifth and sixthcheck valves associated with the third and fourth hydraulic chambers,respectively, are also coupled at least indirectly between thosechambers and the hydraulic motor, and wherein the fifth and sixth checkvalves are configured to allow hydraulic fluid to only flow from thethird and fourth hydraulic chambers to the hydraulic motor.
 8. Theinternal combustion engine of claim 7, wherein seventh and eighth checkvalves associated with the first and second hydraulic chambers,respectively, are coupled between those chambers and a hydraulicreservoir, wherein the hydraulic motor is additionally coupled to thehydraulic reservoir, wherein the seventh and eighth check valves areconfigured to allow hydraulic fluid to only flow from the hydraulicreservoir to the first and second hydraulic chambers, and wherein the atleast one hydraulic link includes the first, second, third, fourth,fifth and sixth valves, as well as the intermediary link and at leastone of the third and fourth hydraulic chambers.
 9. The internalcombustion engine of claim 1, wherein the first and second cylinders arealigned along a first axis and the third and fourth cylinders arealigned along a second axis, wherein the first and second axis are atleast one of parallel to one another and perpendicular to one another,wherein the first and second pistons are rigidly coupled to one anotherby way of a connector tube that extends between the pistons and intoeach of the first and second cylinders, and wherein the first hydraulicchamber is linked to the second hydraulic chamber by an intermediatepassageway through which extends the connector tube, and wherein thefirst hydraulic chamber is sealed from the second hydraulic chamber atleast in part by at least one sealing ring positioned between anexterior surface of the connector tube and an interior surface of theintermediate passageway.
 10. The internal combustion engine of claim 1,further comprising first and second sensing devices associated with thefirst and second cylinders and capable of outputting first and secondsignals, respectively, that are indicative of when the respective firstand second pistons are within first and second positional ranges,respectively, and wherein the sensing devices are selected from thegroup consisting of proximity sensors, capacitance sensors, magneticsensors, and optical sensors.
 11. The internal combustion engine ofclaim 10, wherein the first and second sensing devices are capacitancesensors, wherein the first and second signals respectively are first andsecond capacitance signals indicative of capacitances existing betweenrespective first and second dashpot components and the respective firstand second connector tube collars that are output from the first andsecond dashpot components, respectively, the capacitances varying withrelative distances between the corresponding connector tube collars andthe dashpot components, and wherein the respective first and seconddashpot components are insulated relative to remaining portions of thefirst and second cylinders by way of first and second insulating rings,respectively, and insulated relative to the respective connector tubecollars by way of hydraulic fluid.
 12. The internal combustion engine ofclaim 1 further comprising: electronic control circuitry that is furtherconfigured to monitor position sensing signals relating to positioningof at least one of the first and second pistons within the first andsecond cylinders, and to control the actuation of the intake valves,exhaust valves, fuel injectors and sparking devices based upon theposition sensing signals; and an air tank, wherein the electroniccontrol circuitry only commences operation of the engine upondetermining that a desired level of air pressure exists in the air tank,and upon receiving an operator command to commence operation.
 13. Theinternal combustion engine of claim 12, wherein the electronic controlcircuitry of the engine causes a braking valve to direct hydraulic fluidto flow into a hydraulic accumulator for storage therein in response toreceiving an operator braking command, and wherein the electroniccontrol circuitry causes a re-acceleration valve to direct the hydraulicfluid stored within the hydraulic accumulator back to an input terminalof the motor in response to receiving an operator acceleration command.14. The internal combustion engine of claim 1, wherein the engine iscapable of operating without at least one of a starter and a flywheel.15. The internal combustion engine of claim 1, wherein opening of thefirst intake valve is achieved by actuating an electrically-actuatedsolenoid valve so as to allow some of the compressed air to contact aportion of the first intake valve and consequently cause movement of thefirst intake valve.
 16. An internal combustion engine comprising: afirst piston provided within a first cylinder, wherein a firstcombustion chamber is defined within the cylinder at least in part by aface of the piston; a first intake valve within the first cylindercapable of allowing access to the first combustion chamber; a secondcylinder and a second piston within the second cylinder, wherein asecond combustion chamber and a second hydraulic chamber are formedwithin the second cylinder, wherein the second piston is positionedbetween the second combustion chamber and the second hydraulic chamber,and wherein the second piston is coupled to the first piston by way of aconnector tube in a back-to-back manner such that enlargement of thefirst combustion chamber in response to a combustion event therewithincauses corresponding enlargement of the second hydraulic chamber andreductions in sizes of the first hydraulic chamber and the secondcombustion chamber; and a source of compressed air, wherein the sourceis external of the first cylinder and is coupled to the cylinder by wayof the first intake valve, wherein the first piston does not everoperate so as to compress therewithin an amount of uncombusted fuel/airmixture, whereby the engine is capable of operating without a starter.17. The internal combustion engine of claim 16, further comprising anelectrically-controllable valve that governs communication of thecompressed air from the source to a plunger associated with the firstintake valve, wherein actuation of the electrically-controllable valvecauses the compressed air to be applied to the plunger and thereby causea movement of the first intake valve, wherein additionally a firsthydraulic chamber is defined within the first cylinder at leastpartially by a side of the first piston opposite the face of the piston,and wherein movement of the first piston results in at least one ofhydraulic fluid to be drawn into the hydraulic chamber or forced out ofthe hydraulic chamber.
 18. In an internal combustion engine, the methodcomprising: (a) providing a cylinder assembly having first and secondcylinders and a piston assembly including first and second pistons thatare coupled to one another by rigid structure and positioned within thefirst and second cylinders, respectively, wherein inner and outerchambers are formed within each of the first and second cylinders, theinner chambers being positioned inwardly of the respective pistons alongthe rigid structure and outer chambers being positioned outwardly of therespective pistons relative to the inner chambers, and wherein the innerchambers are configured to receive hydraulic fluid while the outerchambers are configured to receive amounts of fuel and air; (b) causinga first exhaust valve associated with the outer chamber of the firstcylinder to close and a second exhaust valve associated with the outerchamber of the second cylinder to open; (c) opening a first intake valveassociated with the outer chamber of the first cylinder to open; (d)providing compressed air along with fuel into the outer chamber of thefirst cylinder upon the opening of the first intake valve; (e) closingthe first intake valve; (f) causing a combustion event to occur withinthe outer chamber of the first cylinder, the combustion event tending todrive the piston assembly in a manner tending to expand the outerchamber of the first cylinder; and (g) causing the first exhaust valveassociated with the outer chamber of the first cylinder to open and thesecond exhaust valve associated with the outer chamber of the secondcylinder to close.
 19. The method of claim 18, further comprisingsensing at least one EOT position by way of a capacitance signalreceived from an electrode associated with a dashpot assembly, whereinthe engine is capable of determining whether the first piston hasreached a first of the at least one EOT position and whether the secondpiston has reached a second of the at least one EOT position, wherein(c)-(f) are repeated if it is determined that the second piston is nowat the second EOT position and was previously at the second EOT positionprior to initially performing (c)-(f); and wherein (c)-(f) occur if atleast one of the following is true: (i) it is determined that the secondpiston is now at the second EOT position; (ii) it is determined that thefirst piston is not currently at the first EOT position and the secondpiston is not currently at the second EOT position, and furtherdetermined that a predetermined amount of time following an activationof a sparking device has passed.
 20. The method of claim 18, furthercomprising: (h) opening a second intake valve associated with the outerchamber of the second cylinder to open; (i) providing compressed airalong with fuel into the outer chamber of the second cylinder upon theopening of the second intake valve; (j) closing the second intake valve;and (k) causing a combustion event to occur within the outer chamber ofthe second cylinder, the combustion event tending to drive the pistonassembly in a manner tending to expand the outer chamber of the secondcylinder, wherein the internal combustion engine includes electroniccontrol circuitry including right and left latches, and wherein (g)occurs following a switching of statuses of the right and left latches.